diff --git a/changelog.d/6449.bugfix b/changelog.d/6449.bugfix
new file mode 100644
index 00000000000..203b01a0eb3
--- /dev/null
+++ b/changelog.d/6449.bugfix
@@ -0,0 +1 @@
+Extended file name support to include characters from multiple languages, including Cyrillic and Han scripts. ([#6449](https://github.com/element-hq/element-android/issues/6449))
diff --git a/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/internal/util/FileUtilTest.kt b/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/internal/util/FileUtilTest.kt
new file mode 100644
index 00000000000..edcd3095fa8
--- /dev/null
+++ b/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/internal/util/FileUtilTest.kt
@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2024 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.internal.util
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.matrix.android.sdk.InstrumentedTest
+import org.matrix.android.sdk.internal.session.DefaultFileService.Companion.DEFAULT_FILENAME
+import org.matrix.android.sdk.internal.util.file.safeFileName
+
+/**
+ * These tests are run on an Android device because they need to use the static
+ * MimeTypeMap#getSingleton() method, which was failing in the unit test directory.
+ */
+@RunWith(AndroidJUnit4::class)
+class FileUtilTest : InstrumentedTest {
+
+    @Test
+    fun shouldReturnOriginalFilenameWhenValidCharactersAreUsed() {
+        val fileName = "validFileName.txt"
+        val mimeType = "text/plain"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("validFileName.txt", result)
+    }
+
+    @Test
+    fun shouldReplaceInvalidCharactersWithUnderscores() {
+        val fileName = "invalid/filename:with*chars?.txt"
+        val mimeType = "text/plain"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("invalid/filename_with_chars_.txt", result)
+    }
+
+    @Test
+    fun shouldAllowCyrillicCharactersInTheFilename() {
+        val fileName = "тестовыйФайл.txt"
+        val mimeType = "text/plain"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("тестовыйФайл.txt", result)
+    }
+
+    @Test
+    fun shouldAllowHanCharactersInTheFilename() {
+        val fileName = "测试文件.txt"
+        val mimeType = "text/plain"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("测试文件.txt", result)
+    }
+
+    @Test
+    fun shouldReturnDefaultFilenameWhenInputIsNull() {
+        val fileName = null
+        val mimeType = "text/plain"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("$DEFAULT_FILENAME.txt", result)
+    }
+
+    @Test
+    fun shouldAddTheCorrectExtensionWhenMissing() {
+        val fileName = "myDocument"
+        val mimeType = "application/pdf"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("myDocument.pdf", result)
+    }
+
+    @Test
+    fun shouldReplaceInvalidCharactersAndAddTheCorrectExtension() {
+        val fileName = "my*docu/ment"
+        val mimeType = "application/pdf"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("my_docu/ment.pdf", result)
+    }
+
+    @Test
+    fun shouldNotModifyTheExtensionIfItMatchesTheMimeType() {
+        val fileName = "report.pdf"
+        val mimeType = "application/pdf"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("report.pdf", result)
+    }
+
+    @Test
+    fun shouldReplaceSpacesWithUnderscores() {
+        val fileName = "my report.doc"
+        val mimeType = "application/msword"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("my_report.doc", result)
+    }
+
+    @Test
+    fun shouldAppendExtensionIfFileNameHasNoneAndMimeTypeIsValid() {
+        val fileName = "newfile"
+        val mimeType = "image/jpeg"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("newfile.jpg", result)
+    }
+
+    @Test
+    fun shouldKeepHyphenatedNamesIntact() {
+        val fileName = "my-file-name"
+        val mimeType = "application/octet-stream"
+        val result = safeFileName(fileName, mimeType)
+        assertEquals("my-file-name.bin", result)
+    }
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/DefaultFileService.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/DefaultFileService.kt
index 217ef438211..cc11f0e1b92 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/DefaultFileService.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/DefaultFileService.kt
@@ -41,6 +41,7 @@ import org.matrix.android.sdk.internal.network.httpclient.addAuthenticationHeade
 import org.matrix.android.sdk.internal.network.token.AccessTokenProvider
 import org.matrix.android.sdk.internal.session.download.DownloadProgressInterceptor.Companion.DOWNLOAD_PROGRESS_INTERCEPTOR_HEADER
 import org.matrix.android.sdk.internal.util.file.AtomicFileCreator
+import org.matrix.android.sdk.internal.util.file.safeFileName
 import org.matrix.android.sdk.internal.util.time.Clock
 import org.matrix.android.sdk.internal.util.writeToFile
 import timber.log.Timber
@@ -247,28 +248,6 @@ internal class DefaultFileService @Inject constructor(
         }
     }
 
-    private fun safeFileName(fileName: String?, mimeType: String?): String {
-        return buildString {
-            // filename has to be safe for the Android System
-            val result = fileName
-                    ?.replace("[^a-z A-Z0-9\\\\.\\-]".toRegex(), "_")
-                    ?.takeIf { it.isNotEmpty() }
-                    ?: DEFAULT_FILENAME
-            append(result)
-            // Check that the extension is correct regarding the mimeType
-            val extensionFromMime = mimeType?.let { MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType) }
-            if (extensionFromMime != null) {
-                // Compare
-                val fileExtension = result.substringAfterLast(delimiter = ".", missingDelimiterValue = "")
-                if (fileExtension.isEmpty() || fileExtension != extensionFromMime) {
-                    // Missing extension, or diff in extension, add the one provided by the mimetype
-                    append(".")
-                    append(extensionFromMime)
-                }
-            }
-        }
-    }
-
     override fun isFileInCache(
             mxcUrl: String?,
             fileName: String,
@@ -368,6 +347,6 @@ internal class DefaultFileService @Inject constructor(
         private const val ENCRYPTED_FILENAME = "encrypted.bin"
 
         // The extension would be added from the mimetype
-        private const val DEFAULT_FILENAME = "file"
+        const val DEFAULT_FILENAME = "file"
     }
 }
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/util/file/FileUtil.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/util/file/FileUtil.kt
new file mode 100644
index 00000000000..494f55b2dc0
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/util/file/FileUtil.kt
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2024 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.internal.util.file
+
+import android.webkit.MimeTypeMap
+import org.matrix.android.sdk.internal.session.DefaultFileService.Companion.DEFAULT_FILENAME
+import timber.log.Timber
+
+/**
+ * Remove any characters from the file name that are not supported by the Android OS,
+ * and update the file extension to match the mimeType.
+ */
+fun safeFileName(fileName: String?, mimeType: String?): String {
+    return buildString {
+        // filename has to be safe for the Android System
+        val result = fileName
+                ?.replace("[\\\\?%*:|\"<>\\s]".toRegex(), "_")
+                ?.takeIf { it.isNotEmpty() }
+                ?: DEFAULT_FILENAME
+        append(result)
+        // Check that the extension is correct regarding the mimeType
+        val extensionFromMime = mimeType?.let { MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType) }
+        if (extensionFromMime != null) {
+            // Compare
+            val fileExtension = result.substringAfterLast(delimiter = ".", missingDelimiterValue = "")
+            if (fileExtension.isEmpty() || fileExtension != extensionFromMime) {
+                // Missing extension, or diff in extension, add the one provided by the mimetype
+                append(".")
+                append(extensionFromMime)
+            }
+        }
+    }
+}