diff --git a/docs/processes/release/tasks/versions.md b/docs/processes/release/tasks/versions.md
index 454c6b3ace4..719a1044eec 100644
--- a/docs/processes/release/tasks/versions.md
+++ b/docs/processes/release/tasks/versions.md
@@ -204,7 +204,7 @@ The command requires a version number string that follows the typical Java / Mav
     This can be done by running the following command:
 
     ```
-    mvn versions:set-property -DnewVersion=74 -Dproperty=icu.major.version
+    mvn versions:set-property -DnewVersion=74 -Dproperty=icu.major.version -DgenerateBackupPoms=false
     ```
 
     This should happen at the same time and along with the work in the previous step for the version number
diff --git a/icu4c/source/allinone/Build.Windows.IcuVersion.props b/icu4c/source/allinone/Build.Windows.IcuVersion.props
index 7cfed86463c..53a09d90b29 100644
--- a/icu4c/source/allinone/Build.Windows.IcuVersion.props
+++ b/icu4c/source/allinone/Build.Windows.IcuVersion.props
@@ -3,6 +3,6 @@
 <Project ToolsVersion="14.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <!-- This file is used to set the ICU Major Version number, which is used as a suffix on various file names in other Visual Studio projects. -->
   <PropertyGroup>
-    <IcuMajorVersion>77</IcuMajorVersion>
+    <IcuMajorVersion>78</IcuMajorVersion>
   </PropertyGroup>
 </Project>
diff --git a/icu4c/source/common/unicode/uvernum.h b/icu4c/source/common/unicode/uvernum.h
index 847c49f4cfb..f87a4bd893d 100644
--- a/icu4c/source/common/unicode/uvernum.h
+++ b/icu4c/source/common/unicode/uvernum.h
@@ -53,19 +53,19 @@
  *  This value will change in the subsequent releases of ICU
  *  @stable ICU 2.4
  */
-#define U_ICU_VERSION_MAJOR_NUM 77
+#define U_ICU_VERSION_MAJOR_NUM 78
 
 /** The current ICU minor version as an integer.
  *  This value will change in the subsequent releases of ICU
  *  @stable ICU 2.6
  */
-#define U_ICU_VERSION_MINOR_NUM 1
+#define U_ICU_VERSION_MINOR_NUM 0
 
 /** The current ICU patchlevel version as an integer.
  *  This value will change in the subsequent releases of ICU
  *  @stable ICU 2.4
  */
-#define U_ICU_VERSION_PATCHLEVEL_NUM 0
+#define U_ICU_VERSION_PATCHLEVEL_NUM 1
 
 /** The current ICU build level version as an integer.
  *  This value is for use by ICU clients. It defaults to 0.
@@ -79,7 +79,7 @@
  *  This value will change in the subsequent releases of ICU
  *  @stable ICU 2.6
  */
-#define U_ICU_VERSION_SUFFIX _77
+#define U_ICU_VERSION_SUFFIX _78
 
 /**
  * \def U_DEF2_ICU_ENTRY_POINT_RENAME
@@ -132,7 +132,7 @@
  *  This value will change in the subsequent releases of ICU
  *  @stable ICU 2.4
  */
-#define U_ICU_VERSION "77.1"
+#define U_ICU_VERSION "78.0.1"
 
 /**
  * The current ICU library major version number as a string, for library name suffixes.
@@ -145,13 +145,13 @@
  *
  * @stable ICU 2.6
  */
-#define U_ICU_VERSION_SHORT "77"
+#define U_ICU_VERSION_SHORT "78"
 
 #ifndef U_HIDE_INTERNAL_API
 /** Data version in ICU4C.
  * @internal ICU 4.4 Internal Use Only
  **/
-#define U_ICU_DATA_VERSION "77.1"
+#define U_ICU_DATA_VERSION "78.0.1"
 #endif  /* U_HIDE_INTERNAL_API */
 
 /*===========================================================================
diff --git a/icu4c/source/configure b/icu4c/source/configure
index 5bac9bf59d3..9c4c84ff005 100755
--- a/icu4c/source/configure
+++ b/icu4c/source/configure
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.72 for ICU 77.1.
+# Generated by GNU Autoconf 2.72 for ICU 78.0.1.
 #
 # Report bugs to <https://icu.unicode.org/bugs>.
 #
@@ -606,8 +606,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='ICU'
 PACKAGE_TARNAME='icu4c'
-PACKAGE_VERSION='77.1'
-PACKAGE_STRING='ICU 77.1'
+PACKAGE_VERSION='78.0.1'
+PACKAGE_STRING='ICU 78.0.1'
 PACKAGE_BUGREPORT='https://icu.unicode.org/bugs'
 PACKAGE_URL='https://icu.unicode.org/'
 
@@ -1387,7 +1387,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-'configure' configures ICU 77.1 to adapt to many kinds of systems.
+'configure' configures ICU 78.0.1 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1453,7 +1453,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of ICU 77.1:";;
+     short | recursive ) echo "Configuration of ICU 78.0.1:";;
    esac
   cat <<\_ACEOF
 
@@ -1592,7 +1592,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-ICU configure 77.1
+ICU configure 78.0.1
 generated by GNU Autoconf 2.72
 
 Copyright (C) 2023 Free Software Foundation, Inc.
@@ -2184,7 +2184,7 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by ICU $as_me 77.1, which was
+It was created by ICU $as_me 78.0.1, which was
 generated by GNU Autoconf 2.72.  Invocation command line was
 
   $ $0$ac_configure_args_raw
@@ -9019,7 +9019,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by ICU $as_me 77.1, which was
+This file was extended by ICU $as_me 78.0.1, which was
 generated by GNU Autoconf 2.72.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -9075,7 +9075,7 @@ ac_cs_config_escaped=`printf "%s\n" "$ac_cs_config" | sed "s/^ //; s/'/'\\\\\\\\
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config='$ac_cs_config_escaped'
 ac_cs_version="\\
-ICU config.status 77.1
+ICU config.status 78.0.1
 configured by $0, generated by GNU Autoconf 2.72,
   with options \\"\$ac_cs_config\\"
 
diff --git a/icu4c/source/data/makedata.mak b/icu4c/source/data/makedata.mak
index b9ea7a1ba64..1fe8c88593c 100644
--- a/icu4c/source/data/makedata.mak
+++ b/icu4c/source/data/makedata.mak
@@ -12,11 +12,11 @@
 
 ##############################################################################
 # Keep the following in sync with the version - see common/unicode/uvernum.h
-U_ICUDATA_NAME=icudt77
+U_ICUDATA_NAME=icudt78
 ##############################################################################
 !IF "$(UWP)" == "UWP"
 # Optionally change the name of the data file for the UWP version.
-U_ICUDATA_NAME=icudt77
+U_ICUDATA_NAME=icudt78
 !ENDIF
 U_ICUDATA_ENDIAN_SUFFIX=l
 UNICODE_VERSION=16.0
diff --git a/icu4c/source/data/misc/icuver.txt b/icu4c/source/data/misc/icuver.txt
index 0dd57873f05..1119b8559bf 100644
--- a/icu4c/source/data/misc/icuver.txt
+++ b/icu4c/source/data/misc/icuver.txt
@@ -9,6 +9,6 @@
 // ***************************************************************************
 icuver:table(nofallback){
     CLDRVersion{"47"}
-    DataVersion{"77.1.0.0"}
-    ICUVersion{"77.1.0.0"}
+    DataVersion{"78.0.1.0"}
+    ICUVersion{"78.0.1.0"}
 }
diff --git a/icu4j/demos/pom.xml b/icu4j/demos/pom.xml
index eb3883db7ba..15b110f4c5a 100644
--- a/icu4j/demos/pom.xml
+++ b/icu4j/demos/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
   </parent>
 
   <artifactId>demos</artifactId>
diff --git a/icu4j/main/charset/pom.xml b/icu4j/main/charset/pom.xml
index e06a3a1a580..979c2132dd1 100644
--- a/icu4j/main/charset/pom.xml
+++ b/icu4j/main/charset/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/collate/pom.xml b/icu4j/main/collate/pom.xml
index 56abb848fbe..1f2a2844328 100644
--- a/icu4j/main/collate/pom.xml
+++ b/icu4j/main/collate/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/common_tests/pom.xml b/icu4j/main/common_tests/pom.xml
index f005ec3684f..41a92a45401 100644
--- a/icu4j/main/common_tests/pom.xml
+++ b/icu4j/main/common_tests/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/core/pom.xml b/icu4j/main/core/pom.xml
index 70cfc138a6e..c1c90d30e50 100644
--- a/icu4j/main/core/pom.xml
+++ b/icu4j/main/core/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/core/src/main/java/com/ibm/icu/util/VersionInfo.java b/icu4j/main/core/src/main/java/com/ibm/icu/util/VersionInfo.java
index 69ab709a922..b4b36f331dd 100644
--- a/icu4j/main/core/src/main/java/com/ibm/icu/util/VersionInfo.java
+++ b/icu4j/main/core/src/main/java/com/ibm/icu/util/VersionInfo.java
@@ -239,7 +239,7 @@ public final class VersionInfo implements Comparable<VersionInfo>
      * @deprecated This API is ICU internal only.
      */
     @Deprecated
-    public static final String ICU_DATA_VERSION_PATH = "77b";
+    public static final String ICU_DATA_VERSION_PATH = "78b";
 
     /**
      * Data version in ICU4J.
@@ -584,7 +584,7 @@ public final class VersionInfo implements Comparable<VersionInfo>
         UNICODE_15_1   = getInstance(15, 1, 0, 0);
         UNICODE_16_0   = getInstance(16, 0, 0, 0);
 
-        ICU_VERSION   = getInstance(77, 1, 0, 0);
+        ICU_VERSION   = getInstance(78, 0, 1, 0);
         ICU_DATA_VERSION = ICU_VERSION;
         UNICODE_VERSION = UNICODE_16_0;
 
diff --git a/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/util/DebugUtilitiesData.java b/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/util/DebugUtilitiesData.java
index 08aa6f7d9b0..48ac8d1e1cb 100644
--- a/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/util/DebugUtilitiesData.java
+++ b/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/util/DebugUtilitiesData.java
@@ -10,7 +10,7 @@
 package com.ibm.icu.dev.test.util;
 
 public class DebugUtilitiesData extends Object {
-    public static final String ICU4C_VERSION="77.1";
+    public static final String ICU4C_VERSION="78.0.1";
     public static final int UDebugEnumType = 0;
     public static final int UCalendarDateFields = 1;
     public static final int UCalendarMonths = 2;
diff --git a/icu4j/main/currdata/pom.xml b/icu4j/main/currdata/pom.xml
index 23612a79882..22542596485 100644
--- a/icu4j/main/currdata/pom.xml
+++ b/icu4j/main/currdata/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/framework/pom.xml b/icu4j/main/framework/pom.xml
index 01e88658973..3bc197f8d6d 100644
--- a/icu4j/main/framework/pom.xml
+++ b/icu4j/main/framework/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/icu4j/pom.xml b/icu4j/main/icu4j/pom.xml
index a99d4960138..f0f42f9729b 100644
--- a/icu4j/main/icu4j/pom.xml
+++ b/icu4j/main/icu4j/pom.xml
@@ -9,7 +9,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/langdata/pom.xml b/icu4j/main/langdata/pom.xml
index bfe912bff8e..362eb83e7c9 100644
--- a/icu4j/main/langdata/pom.xml
+++ b/icu4j/main/langdata/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/localespi/pom.xml b/icu4j/main/localespi/pom.xml
index 0be523ab662..f2a956f7fad 100644
--- a/icu4j/main/localespi/pom.xml
+++ b/icu4j/main/localespi/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/regiondata/pom.xml b/icu4j/main/regiondata/pom.xml
index 8e5e51fec9d..7199b5d15d5 100644
--- a/icu4j/main/regiondata/pom.xml
+++ b/icu4j/main/regiondata/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/main/translit/pom.xml b/icu4j/main/translit/pom.xml
index f040bce8c6e..fd6896fdd44 100644
--- a/icu4j/main/translit/pom.xml
+++ b/icu4j/main/translit/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/perf-tests/pom.xml b/icu4j/perf-tests/pom.xml
index 3767dd0580e..a4debcade13 100644
--- a/icu4j/perf-tests/pom.xml
+++ b/icu4j/perf-tests/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
   </parent>
 
   <artifactId>perf-tests</artifactId>
diff --git a/icu4j/pom.xml b/icu4j/pom.xml
index a18ed93a073..fbf4e94f64c 100644
--- a/icu4j/pom.xml
+++ b/icu4j/pom.xml
@@ -8,7 +8,7 @@
 
   <groupId>com.ibm.icu</groupId>
   <artifactId>icu4j-root</artifactId>
-  <version>77.1</version>
+  <version>78.0.1-SNAPSHOT</version>
   <packaging>pom</packaging>
 
   <name>${proj-title} (${project.artifactId})</name>
@@ -72,7 +72,7 @@
     <proj.scm.url>https://github.com/unicode-org/icu</proj.scm.url>
 
     <!-- Version update! -->
-    <icu.major.version>77</icu.major.version>
+    <icu.major.version>78</icu.major.version>
 
     <!-- Variables used to generate the javadoc -->
     <!-- Version update! -->
diff --git a/icu4j/releases_tools/shared.sh b/icu4j/releases_tools/shared.sh
index 1b7f82c1855..bed1920c37c 100755
--- a/icu4j/releases_tools/shared.sh
+++ b/icu4j/releases_tools/shared.sh
@@ -5,10 +5,10 @@
 export MAVEN_ARGS='--no-transfer-progress'
 
 # Version update!
-export artifact_version='77.1'
-export github_rel_version='77_1'
-export api_report_version='77'
-export api_report_prev_version='76'
+export artifact_version='78.0.1-SNAPSHOT'
+export github_rel_version='78_0_1'
+export api_report_version='78'
+export api_report_prev_version='77'
 export out_dir=target
 
 function checkThatJdk8IsNotDefault() {
diff --git a/icu4j/samples/pom.xml b/icu4j/samples/pom.xml
index 6dee7737102..2c75ed9d8f8 100644
--- a/icu4j/samples/pom.xml
+++ b/icu4j/samples/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
   </parent>
 
   <artifactId>samples</artifactId>
diff --git a/icu4j/tools/build/pom.xml b/icu4j/tools/build/pom.xml
index 98b0382c2f5..edee524870b 100644
--- a/icu4j/tools/build/pom.xml
+++ b/icu4j/tools/build/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/tools/misc/pom.xml b/icu4j/tools/misc/pom.xml
index b4ee188eae7..dab6a6254e9 100644
--- a/icu4j/tools/misc/pom.xml
+++ b/icu4j/tools/misc/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/icu4j/tools/taglets/pom.xml b/icu4j/tools/taglets/pom.xml
index 2a39ef40a4d..6c6ba9d591e 100644
--- a/icu4j/tools/taglets/pom.xml
+++ b/icu4j/tools/taglets/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.ibm.icu</groupId>
     <artifactId>icu4j-root</artifactId>
-    <version>77.1</version>
+    <version>78.0.1-SNAPSHOT</version>
     <relativePath>../../pom.xml</relativePath>
   </parent>
 
diff --git a/tools/cldr/cldr-to-icu/pom.xml b/tools/cldr/cldr-to-icu/pom.xml
index 93accd02f32..90f99b99f33 100644
--- a/tools/cldr/cldr-to-icu/pom.xml
+++ b/tools/cldr/cldr-to-icu/pom.xml
@@ -20,8 +20,8 @@
         <maven.compiler.source>11</maven.compiler.source>
         <maven.compiler.target>11</maven.compiler.target>
 
-        <icu4j.version>77.1</icu4j.version>
-        <cldr-code.version>47.0-SNAPSHOT</cldr-code.version>
+        <icu4j.version>78.0.1-SNAPSHOT</icu4j.version>
+        <cldr-code.version>48.0-SNAPSHOT</cldr-code.version>
         <guava.version>32.1.1-jre</guava.version>
         <truth.version>1.4.4</truth.version>
         <commons-cli.version>1.9.0</commons-cli.version>