diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c445d6..a692fe8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- Support Windows11 26H1.
+
 ### Changed
 
 - Upgrade .NET8 to .NET10.
diff --git a/README-en.md b/README-en.md
index c159f9f..15e2b5a 100644
--- a/README-en.md
+++ b/README-en.md
@@ -165,6 +165,7 @@ A screen for selecting a database file will open, so specify the database file (
   - Version 23H2
   - Version 24H2
   - Version 25H2
+  - Version 26H1
 
 ## Restrictions
 - When logged in via remote desktop, the user name cannot be obtained and is recorded as "Unknown".
diff --git a/README.md b/README.md
index cc338c3..5873dac 100644
--- a/README.md
+++ b/README.md
@@ -165,6 +165,7 @@ WindowsDeviceManagerViewerフォルダ内のWindowsDeviceManagerViewer.exeを起
   - Version 23H2
   - Version 24H2
   - Version 25H2
+  - Version 26H1
 
 ## 制限事項
 - リモートデスクトップでログインしている時は､ユーザ名が取得できないため､｢不明｣と記録されます｡
diff --git a/src/WindowsDeviceManagerAgent/WindowsDeviceInfoCollector.cs b/src/WindowsDeviceManagerAgent/WindowsDeviceInfoCollector.cs
index 0bc5c6a..151c144 100644
--- a/src/WindowsDeviceManagerAgent/WindowsDeviceInfoCollector.cs
+++ b/src/WindowsDeviceManagerAgent/WindowsDeviceInfoCollector.cs
@@ -213,6 +213,7 @@ private static string GetOSVersion()
                         "22631" => "23H2",
                         "26100" => "24H2",
                         "26200" => "25H2",
+                        "28000" => "26H1",
                         _ => $"{Resources.Strings.Unknown}(OS Build:{osBuildNumber})"
                     };
                 }
diff --git a/src/WindowsDeviceManagerViewer/Utilities/DatabaseWriter.cs b/src/WindowsDeviceManagerViewer/Utilities/DatabaseWriter.cs
index 4ac2767..8b5f940 100644
--- a/src/WindowsDeviceManagerViewer/Utilities/DatabaseWriter.cs
+++ b/src/WindowsDeviceManagerViewer/Utilities/DatabaseWriter.cs
@@ -180,6 +180,7 @@ private static string GetOSVersion(string osName, string osBuildNumber)
                     "22631" => "23H2",
                     "26100" => "24H2",
                     "26200" => "25H2",
+                    "28000" => "26H1",
                     _ => $"{Resources.Strings.Unknown}(OS Build:{osBuildNumber})"
                 };
             }