diff --git a/change/@office-iss-react-native-win32-243153c9-8988-4102-9d22-7b100e46cc61.json b/change/@office-iss-react-native-win32-243153c9-8988-4102-9d22-7b100e46cc61.json
new file mode 100644
index 00000000000..4a0da1cbeae
--- /dev/null
+++ b/change/@office-iss-react-native-win32-243153c9-8988-4102-9d22-7b100e46cc61.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@office-iss/react-native-win32",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-automation-03834cb8-1e4d-4b59-88d0-a9d559be3ff3.json b/change/@react-native-windows-automation-03834cb8-1e4d-4b59-88d0-a9d559be3ff3.json
new file mode 100644
index 00000000000..cb8bea2c95f
--- /dev/null
+++ b/change/@react-native-windows-automation-03834cb8-1e4d-4b59-88d0-a9d559be3ff3.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/automation",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-automation-channel-539c03f5-4d34-4e4f-9206-a32e1385f81c.json b/change/@react-native-windows-automation-channel-539c03f5-4d34-4e4f-9206-a32e1385f81c.json
new file mode 100644
index 00000000000..bad12a08d86
--- /dev/null
+++ b/change/@react-native-windows-automation-channel-539c03f5-4d34-4e4f-9206-a32e1385f81c.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/automation-channel",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-automation-commands-77fc40fb-86cd-4cb3-826a-71642851095a.json b/change/@react-native-windows-automation-commands-77fc40fb-86cd-4cb3-826a-71642851095a.json
new file mode 100644
index 00000000000..e1de0b0590b
--- /dev/null
+++ b/change/@react-native-windows-automation-commands-77fc40fb-86cd-4cb3-826a-71642851095a.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/automation-commands",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-cli-4809a750-62f5-4f63-ab84-5d216a89ae8e.json b/change/@react-native-windows-cli-4809a750-62f5-4f63-ab84-5d216a89ae8e.json
new file mode 100644
index 00000000000..05a531acc58
--- /dev/null
+++ b/change/@react-native-windows-cli-4809a750-62f5-4f63-ab84-5d216a89ae8e.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/cli",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-codegen-840c2cd5-5181-43ac-a396-bca2f2672c22.json b/change/@react-native-windows-codegen-840c2cd5-5181-43ac-a396-bca2f2672c22.json
new file mode 100644
index 00000000000..cbfc5606902
--- /dev/null
+++ b/change/@react-native-windows-codegen-840c2cd5-5181-43ac-a396-bca2f2672c22.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/codegen",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-find-dotnet-tools-329eaf92-c8a6-4f3a-8b28-360ccfc1bfce.json b/change/@react-native-windows-find-dotnet-tools-329eaf92-c8a6-4f3a-8b28-360ccfc1bfce.json
new file mode 100644
index 00000000000..570b587102a
--- /dev/null
+++ b/change/@react-native-windows-find-dotnet-tools-329eaf92-c8a6-4f3a-8b28-360ccfc1bfce.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/find-dotnet-tools",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-find-repo-root-faf214cb-fbea-4d0a-a9fd-13b6b0756c25.json b/change/@react-native-windows-find-repo-root-faf214cb-fbea-4d0a-a9fd-13b6b0756c25.json
new file mode 100644
index 00000000000..403da977189
--- /dev/null
+++ b/change/@react-native-windows-find-repo-root-faf214cb-fbea-4d0a-a9fd-13b6b0756c25.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/find-repo-root",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-fs-601c42e6-2bb4-441b-a130-f3a6d9f68d39.json b/change/@react-native-windows-fs-601c42e6-2bb4-441b-a130-f3a6d9f68d39.json
new file mode 100644
index 00000000000..ee655c50ad5
--- /dev/null
+++ b/change/@react-native-windows-fs-601c42e6-2bb4-441b-a130-f3a6d9f68d39.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/fs",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-package-utils-7711ae4f-4002-4089-bd5d-38f1b1414e88.json b/change/@react-native-windows-package-utils-7711ae4f-4002-4089-bd5d-38f1b1414e88.json
new file mode 100644
index 00000000000..77be99292d2
--- /dev/null
+++ b/change/@react-native-windows-package-utils-7711ae4f-4002-4089-bd5d-38f1b1414e88.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/package-utils",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-perf-testing-2612ab28-0019-4905-a943-17b206e2625f.json b/change/@react-native-windows-perf-testing-2612ab28-0019-4905-a943-17b206e2625f.json
new file mode 100644
index 00000000000..85559124d8c
--- /dev/null
+++ b/change/@react-native-windows-perf-testing-2612ab28-0019-4905-a943-17b206e2625f.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/perf-testing",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@react-native-windows-telemetry-b6d78919-a2db-4462-8bfa-66d5eabcb4be.json b/change/@react-native-windows-telemetry-b6d78919-a2db-4462-8bfa-66d5eabcb4be.json
new file mode 100644
index 00000000000..8b9dc059274
--- /dev/null
+++ b/change/@react-native-windows-telemetry-b6d78919-a2db-4462-8bfa-66d5eabcb4be.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "@react-native-windows/telemetry",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/react-native-platform-override-86771811-a02c-444d-b190-8629e1de72f3.json b/change/react-native-platform-override-86771811-a02c-444d-b190-8629e1de72f3.json
new file mode 100644
index 00000000000..25db22adb34
--- /dev/null
+++ b/change/react-native-platform-override-86771811-a02c-444d-b190-8629e1de72f3.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "react-native-platform-override",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/react-native-windows-b9d80e95-fc88-4715-a2e5-bfc745f713f5.json b/change/react-native-windows-b9d80e95-fc88-4715-a2e5-bfc745f713f5.json
new file mode 100644
index 00000000000..52b84ca4456
--- /dev/null
+++ b/change/react-native-windows-b9d80e95-fc88-4715-a2e5-bfc745f713f5.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "react-native-windows",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/change/react-native-windows-init-7ee112c5-50ea-4a36-aa1f-80f19b7b1135.json b/change/react-native-windows-init-7ee112c5-50ea-4a36-aa1f-80f19b7b1135.json
new file mode 100644
index 00000000000..39ec8b15bbc
--- /dev/null
+++ b/change/react-native-windows-init-7ee112c5-50ea-4a36-aa1f-80f19b7b1135.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Promote 0.84 to legacy",
+  "packageName": "react-native-windows-init",
+  "email": "email not defined",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/@office-iss/react-native-win32/package.json b/packages/@office-iss/react-native-win32/package.json
index 8fbea2a47d7..4c727074964 100644
--- a/packages/@office-iss/react-native-win32/package.json
+++ b/packages/@office-iss/react-native-win32/package.json
@@ -101,7 +101,7 @@
     "react-native": "0.84.1"
   },
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/automation-channel/package.json b/packages/@react-native-windows/automation-channel/package.json
index 0049b374269..3ccb2cd4df9 100644
--- a/packages/@react-native-windows/automation-channel/package.json
+++ b/packages/@react-native-windows/automation-channel/package.json
@@ -43,7 +43,7 @@
     "!packages*.lock.json"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/automation-commands/package.json b/packages/@react-native-windows/automation-commands/package.json
index 06640f9120b..1b815ff5221 100644
--- a/packages/@react-native-windows/automation-commands/package.json
+++ b/packages/@react-native-windows/automation-commands/package.json
@@ -38,7 +38,7 @@
     "README.md"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/automation/package.json b/packages/@react-native-windows/automation/package.json
index 11d184a30bb..0585c461048 100644
--- a/packages/@react-native-windows/automation/package.json
+++ b/packages/@react-native-windows/automation/package.json
@@ -49,7 +49,7 @@
     "README.md"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/cli/package.json b/packages/@react-native-windows/cli/package.json
index e55ca113d59..3255f179143 100644
--- a/packages/@react-native-windows/cli/package.json
+++ b/packages/@react-native-windows/cli/package.json
@@ -74,7 +74,7 @@
     "src/powershell"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/codegen/package.json b/packages/@react-native-windows/codegen/package.json
index 51fdee7e861..fb32666b73b 100644
--- a/packages/@react-native-windows/codegen/package.json
+++ b/packages/@react-native-windows/codegen/package.json
@@ -58,7 +58,7 @@
     "src"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/find-dotnet-tools/package.json b/packages/@react-native-windows/find-dotnet-tools/package.json
index e9eec406371..867eab26e16 100644
--- a/packages/@react-native-windows/find-dotnet-tools/package.json
+++ b/packages/@react-native-windows/find-dotnet-tools/package.json
@@ -31,7 +31,7 @@
     "typescript": "5.0.4"
   },
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/find-repo-root/package.json b/packages/@react-native-windows/find-repo-root/package.json
index 62109c3035d..6deee317529 100644
--- a/packages/@react-native-windows/find-repo-root/package.json
+++ b/packages/@react-native-windows/find-repo-root/package.json
@@ -33,7 +33,7 @@
     "typescript": "5.0.4"
   },
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/fs/package.json b/packages/@react-native-windows/fs/package.json
index c69c349593a..f61b9d2d2ae 100644
--- a/packages/@react-native-windows/fs/package.json
+++ b/packages/@react-native-windows/fs/package.json
@@ -37,7 +37,7 @@
     "lib-commonjs"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/package-utils/package.json b/packages/@react-native-windows/package-utils/package.json
index 0331e3243dd..41d37793efd 100644
--- a/packages/@react-native-windows/package-utils/package.json
+++ b/packages/@react-native-windows/package-utils/package.json
@@ -35,7 +35,7 @@
     "typescript": "5.0.4"
   },
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/perf-testing/package.json b/packages/@react-native-windows/perf-testing/package.json
index 31c5beb41b6..a842187eca2 100644
--- a/packages/@react-native-windows/perf-testing/package.json
+++ b/packages/@react-native-windows/perf-testing/package.json
@@ -50,7 +50,7 @@
     "README.md"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/@react-native-windows/telemetry/package.json b/packages/@react-native-windows/telemetry/package.json
index aa8f2e9e148..037e53a54f7 100644
--- a/packages/@react-native-windows/telemetry/package.json
+++ b/packages/@react-native-windows/telemetry/package.json
@@ -52,7 +52,7 @@
     "lib-commonjs"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/react-native-platform-override/package.json b/packages/react-native-platform-override/package.json
index 72cb47334b1..7199d21f4c7 100644
--- a/packages/react-native-platform-override/package.json
+++ b/packages/react-native-platform-override/package.json
@@ -73,7 +73,7 @@
     "react-native": "*"
   },
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/packages/react-native-windows-init/package.json b/packages/react-native-windows-init/package.json
index 3907f481dbe..18e7a853ef5 100644
--- a/packages/react-native-windows-init/package.json
+++ b/packages/react-native-windows-init/package.json
@@ -62,7 +62,7 @@
     "README.md"
   ],
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",
diff --git a/vnext/package.json b/vnext/package.json
index 7f8c90265b0..da05c136bd9 100644
--- a/vnext/package.json
+++ b/vnext/package.json
@@ -97,7 +97,7 @@
     "react-native": "0.84.1"
   },
   "beachball": {
-    "defaultNpmTag": "latest",
+    "defaultNpmTag": "v0.84-stable",
     "disallowedChangeTypes": [
       "major",
       "minor",