diff --git a/download.lst b/download.lst
index 2d6303869042..a2ce4979764d 100644
--- a/download.lst
+++ b/download.lst
@@ -116,8 +116,8 @@ ETONYEK_TARBALL := libetonyek-0.1.$(ETONYEK_VERSION_MICRO).tar.xz
 # three static lines
 # so that git cherry-pick
 # will not run into conflicts
-EXPAT_SHA256SUM := 1e727b8933ec51a77a9a9d9afcf8e688bce45d907c13e36ab7393fe36e703182
-EXPAT_TARBALL := expat-2.8.5.tar.xz
+EXPAT_SHA256SUM := 1e6371862cc31999b368c3b89b49994f0677e1bab5f1b2b85ae3741f5d803051
+EXPAT_TARBALL := expat-2.9.0.tar.xz
 # three static lines
 # so that git cherry-pick
 # will not run into conflicts
diff --git a/external/expat/0001-fix-XML_GE-is-not-defined-evaluates-to-0-Werror-unde.patch b/external/expat/0001-fix-XML_GE-is-not-defined-evaluates-to-0-Werror-unde.patch
new file mode 100644
index 000000000000..5ac374aec5b6
--- /dev/null
+++ b/external/expat/0001-fix-XML_GE-is-not-defined-evaluates-to-0-Werror-unde.patch
@@ -0,0 +1,25 @@
+From 3e3d9091bc3db29901a1507466bf0479ff38de9a Mon Sep 17 00:00:00 2001
+From: Xisco Fauli <xiscofauli@libreoffice.org>
+Date: Tue, 6 Oct 2026 10:50:50 +0200
+Subject: [PATCH] fix XML_GE is not defined, evaluates to 0 [-Werror=undef]
+
+---
+ expat/lib/expat.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/expat/lib/expat.h b/expat/lib/expat.h
+index 1b2852dd..fea2fd99 100644
+--- a/expat/lib/expat.h
++++ b/expat/lib/expat.h
+@@ -1084,7 +1084,7 @@ enum XML_Parser_Property {
+ #  if defined(XML_TESTING)
+   XML_PROP_INVALID = 0,
+ #  endif
+-#  if XML_GE == 1
++#  if defined(XML_GE) && XML_GE == 1
+   XML_PROP_ALLOC_TRACKER_ACTIVATION_THRESHOLD = 1,   // of type `uint64_t`
+   XML_PROP_ALLOC_TRACKER_MAXIMUM_AMPLIFICATION = 2,  // of type `double`
+   XML_PROP_BILLION_LAUGHS_ACTIVATION_THRESHOLD = 3,  // of type `uint64_t`
+-- 
+2.47.3
+
diff --git a/external/expat/StaticLibrary_expat.mk b/external/expat/StaticLibrary_expat.mk
index 6ca4fc84bf7f..b3b8fbb5d1ed 100644
--- a/external/expat/StaticLibrary_expat.mk
+++ b/external/expat/StaticLibrary_expat.mk
@@ -57,6 +57,7 @@ $(eval $(call gb_StaticLibrary_add_generated_cobjects,expat,\
 endif
 
 $(eval $(call gb_StaticLibrary_add_generated_cobjects,expat,\
+	UnpackedTarball/expat/lib/xcs \
 	UnpackedTarball/expat/lib/xmlparse \
 	UnpackedTarball/expat/lib/xmlrole \
 	UnpackedTarball/expat/lib/xmltok \
diff --git a/external/expat/UnpackedTarball_expat.mk b/external/expat/UnpackedTarball_expat.mk
index e9e4f75046f2..721b9ac6e031 100644
--- a/external/expat/UnpackedTarball_expat.mk
+++ b/external/expat/UnpackedTarball_expat.mk
@@ -17,6 +17,7 @@ $(eval $(call gb_UnpackedTarball_set_patchlevel,expat,2))
 
 $(eval $(call gb_UnpackedTarball_add_patches,expat,\
 	external/expat/expat-winapi.patch \
+	external/expat/0001-fix-XML_GE-is-not-defined-evaluates-to-0-Werror-unde.patch \
 ))
 
 # vim: set noet sw=4 ts=4:
diff --git a/external/expat/expat-winapi.patch b/external/expat/expat-winapi.patch
index ea664c3db76c..a789c7057c50 100644
--- a/external/expat/expat-winapi.patch
+++ b/external/expat/expat-winapi.patch
@@ -13,8 +13,8 @@
  
 --- misc/expat-2.5.0/lib/xmlparse.c	2022-10-26 00:09:08.000000000 +0900
 +++ misc/build/expat-2.5.0/lib/xmlparse.c	2022-10-30 23:09:01.843006341 +0900
-@@ -98,6 +98,10 @@
- #include <errno.h>
+@@ -112,6 +112,10 @@
+ #include <wchar.h> /* wcsncmp */
  
  #ifdef _WIN32
 +#  undef HAVE_ARC4RANDOM
diff --git a/l10ntools/source/xmlparse.cxx b/l10ntools/source/xmlparse.cxx
index 875bdd308a27..be670f0bd27f 100644
--- a/l10ntools/source/xmlparse.cxx
+++ b/l10ntools/source/xmlparse.cxx
@@ -888,8 +888,13 @@ bool SimpleXMLParser::Execute( const OString &rFileName, XMLFile* pXMLFile )
     if (!result)
     {
         m_aErrorInformation.m_eCode = XML_GetErrorCode( m_aParser );
+#if (XML_MAJOR_VERSION > 2 || (XML_MAJOR_VERSION == 2 && XML_MINOR_VERSION >= 9))
+        m_aErrorInformation.m_nLine = XML_GetCurrentLineNumber64( m_aParser );
+        m_aErrorInformation.m_nColumn = XML_GetCurrentColumnNumber64( m_aParser );
+#else
         m_aErrorInformation.m_nLine = XML_GetErrorLineNumber( m_aParser );
         m_aErrorInformation.m_nColumn = XML_GetErrorColumnNumber( m_aParser );
+#endif
 
         m_aErrorInformation.m_sMessage = "ERROR: "_ostr;
         if ( !pXMLFile->GetName().isEmpty())
diff --git a/sax/source/expatwrap/sax_expat.cxx b/sax/source/expatwrap/sax_expat.cxx
index f6e6cdb90f55..d4cd6fa8b0e0 100644
--- a/sax/source/expatwrap/sax_expat.cxx
+++ b/sax/source/expatwrap/sax_expat.cxx
@@ -315,11 +315,19 @@ public:
 public: //XLocator
     virtual sal_Int32 SAL_CALL getColumnNumber() override
     {
+#if (XML_MAJOR_VERSION > 2 || (XML_MAJOR_VERSION == 2 && XML_MINOR_VERSION >= 9))
+        return XML_GetCurrentColumnNumber64( m_pParser->getEntity().pParser );
+#else
         return XML_GetCurrentColumnNumber( m_pParser->getEntity().pParser );
+#endif
     }
     virtual sal_Int32 SAL_CALL getLineNumber() override
     {
+#if (XML_MAJOR_VERSION > 2 || (XML_MAJOR_VERSION == 2 && XML_MINOR_VERSION >= 9))
+        return XML_GetCurrentLineNumber64( m_pParser->getEntity().pParser );
+#else
         return XML_GetCurrentLineNumber( m_pParser->getEntity().pParser );
+#endif
     }
     virtual OUString SAL_CALL getPublicId() override
     {
@@ -337,7 +345,11 @@ public: //XLocator
     }
     virtual sal_Int64 SAL_CALL getPosition() override
     {
+#if (XML_MAJOR_VERSION > 2 || (XML_MAJOR_VERSION == 2 && XML_MINOR_VERSION >= 9))
+        return XML_GetCurrentByteIndex64( m_pParser->getEntity().pParser );
+#else
         return XML_GetCurrentByteIndex( m_pParser->getEntity().pParser );
+#endif
     }
     virtual ::sal_Int64 SAL_CALL getLength() override
     {