diff --git a/bindings/tpython/src/TPython.cxx b/bindings/tpython/src/TPython.cxx
index c9bf9a584c14d..249e5903aded5 100644
--- a/bindings/tpython/src/TPython.cxx
+++ b/bindings/tpython/src/TPython.cxx
@@ -23,12 +23,11 @@
 #include "TClassRef.h"
 #include "TObject.h"
 
-#include <Riostream.h>
-
 // Standard
 #include <mutex>
 #include <sstream>
-#include <stdio.h>
+#include <cstdio>
+#include <iostream>
 #include <string>
 
 /// \class TPython
diff --git a/core/base/inc/TParameter.h b/core/base/inc/TParameter.h
index 945746b52ba75..a6a0edfd2dbf9 100644
--- a/core/base/inc/TParameter.h
+++ b/core/base/inc/TParameter.h
@@ -21,16 +21,13 @@
 //                                                                      //
 //////////////////////////////////////////////////////////////////////////
 
-#include "Riostream.h"
-
 #include "TObject.h"
-
 #include "TCollection.h"
-
 #include "TString.h"
-
 #include "TROOT.h"
 
+#include <iostream>
+
 template <class AParamType>
 class TParameter : public TObject {
 
diff --git a/core/rint/src/TTabCom.cxx b/core/rint/src/TTabCom.cxx
index 8af741db377fb..eaf13ea4b6d92 100644
--- a/core/rint/src/TTabCom.cxx
+++ b/core/rint/src/TTabCom.cxx
@@ -144,10 +144,12 @@
 #include "TFunction.h"
 #include "TMethodArg.h"
 #include "TInterpreter.h"
-#include "Riostream.h"
 #include "Rstrstream.h"
 #include "strlcpy.h"
 
+#include <iostream>
+#include <fstream>
+
 #define BUF_SIZE 1024 // must be smaller than/equal to fgLineBufSize in Getline.cxx and
                       // lineBufSize in cppcompleter.py
 #define IfDebug(x)  if(gDebug==TTabCom::kDebug) x
diff --git a/geom/geom/inc/TGeoVector3.h b/geom/geom/inc/TGeoVector3.h
index 48d99bb8bf9da..07640ec6c5dcf 100644
--- a/geom/geom/inc/TGeoVector3.h
+++ b/geom/geom/inc/TGeoVector3.h
@@ -12,9 +12,10 @@
 #ifndef ROOT_TGeoVector3
 #define ROOT_TGeoVector3
 
-#include <Riostream.h>
 #include <TMath.h>
 
+#include <iosfwd>
+
 namespace ROOT {
 namespace Geom {
 
diff --git a/geom/geom/src/TGeoTessellated.cxx b/geom/geom/src/TGeoTessellated.cxx
index 29f195709028d..aa660785a43c7 100644
--- a/geom/geom/src/TGeoTessellated.cxx
+++ b/geom/geom/src/TGeoTessellated.cxx
@@ -20,6 +20,7 @@ for the composing faces.
 */
 
 #include <iostream>
+#include <fstream>
 #include <sstream>
 
 #include "TGeoManager.h"
diff --git a/geom/geom/src/TGeoVector3.cxx b/geom/geom/src/TGeoVector3.cxx
index f7e7f3c5df3dd..e97cda0fe275a 100644
--- a/geom/geom/src/TGeoVector3.cxx
+++ b/geom/geom/src/TGeoVector3.cxx
@@ -16,6 +16,8 @@ Simple 3-vector representation
 
 #include "TGeoVector3.h"
 
+#include <ostream>
+
 std::ostream &operator<<(std::ostream &os, ROOT::Geom::Vertex_t const &vec)
 {
    os << "{" << vec[0] << ", " << vec[1] << ", " << vec[2] << "}";
diff --git a/gui/gui/src/TGFrame.cxx b/gui/gui/src/TGFrame.cxx
index 710a2e98f802b..cac75c9ed200d 100644
--- a/gui/gui/src/TGFrame.cxx
+++ b/gui/gui/src/TGFrame.cxx
@@ -2895,7 +2895,11 @@ void TGMainFrame::SaveSource(const char *filename, Option_t *option)
       if (strstr(inc->GetString(), "TRootEmbeddedCanvas"))
          out << "#include \"TCanvas.h\"\n";
    }
-   out << "\n#include \"Riostream.h\"\n\n";
+   // Workaround for https://github.com/llvm/llvm-project/issues/138683
+   // Include <chrono> before <fstream> to ensure _FilesystemClock is defined
+   // Can be removed once the upstream issue is fixed.
+   out << "\n#ifdef __APPLE__\n#include <chrono>\n#endif\n\n";
+   out << "\n#include <fstream>\n#include <iostream>\n#include <iomanip>\n\n";
    // deletes created ListOfIncludes
    gROOT->GetListOfSpecials()->Remove(ilist);
    ilist->Delete();
@@ -3344,7 +3348,11 @@ void TGTransientFrame::SaveSource(const char *filename, Option_t *option)
       if (strstr(inc->GetString(), "TRootEmbeddedCanvas"))
          out << "#include \"TCanvas.h\"\n";
    }
-   out << "\n#include \"Riostream.h\"\n\n";
+   // Workaround for https://github.com/llvm/llvm-project/issues/138683
+   // Include <chrono> before <fstream> to ensure _FilesystemClock is defined
+   // Can be removed once the upstream issue is fixed.
+   out << "\n#ifdef __APPLE__\n#include <chrono>\n#endif\n\n";
+   out << "\n#include <fstream>\n#include <iostream>\n#include <iomanip>\n\n";
    // deletes created ListOfIncludes
    gROOT->GetListOfSpecials()->Remove(ilist);
    ilist->Delete();
diff --git a/hist/hist/src/TConfidenceLevel.cxx b/hist/hist/src/TConfidenceLevel.cxx
index da8c995de3ce5..650fd5b5b0475 100644
--- a/hist/hist/src/TConfidenceLevel.cxx
+++ b/hist/hist/src/TConfidenceLevel.cxx
@@ -16,8 +16,8 @@
 #include "TConfidenceLevel.h"
 #include "TH1F.h"
 #include "TMath.h"
-#include "Riostream.h"
 
+#include <iostream>
 
 Double_t const TConfidenceLevel::fgMCLM2S = 0.025;
 Double_t const TConfidenceLevel::fgMCLM1S = 0.16;
diff --git a/hist/hist/src/TF3.cxx b/hist/hist/src/TF3.cxx
index a7d785ca78be7..ac2da231e2db8 100644
--- a/hist/hist/src/TF3.cxx
+++ b/hist/hist/src/TF3.cxx
@@ -16,12 +16,9 @@
 #include "TH3.h"
 #include "TVirtualPad.h"
 #include "TRandom.h"
-#include "TVectorD.h"
-#include "Riostream.h"
-#include "TColor.h"
-#include "TVirtualFitter.h"
 #include "TVirtualHistPainter.h"
 #include "Math/IntegratorOptions.h"
+
 #include <cassert>
 
 
diff --git a/hist/hist/src/TGraphMultiErrors.cxx b/hist/hist/src/TGraphMultiErrors.cxx
index f76010a449287..6d86e9c506dc7 100644
--- a/hist/hist/src/TGraphMultiErrors.cxx
+++ b/hist/hist/src/TGraphMultiErrors.cxx
@@ -13,7 +13,6 @@
 #include "TStyle.h"
 #include "TVirtualPad.h"
 #include "TEfficiency.h"
-#include "Riostream.h"
 
 #include "TArrayD.h"
 #include "TVector.h"
@@ -24,6 +23,8 @@
 
 #include "TGraphMultiErrors.h"
 
+#include <ostream>
+#include <vector>
 
 /** \class TGraphMultiErrors
     \ingroup Graphs
diff --git a/hist/hist/src/TGraphSmooth.cxx b/hist/hist/src/TGraphSmooth.cxx
index 39b36b4c359ea..fa945b341bdd6 100644
--- a/hist/hist/src/TGraphSmooth.cxx
+++ b/hist/hist/src/TGraphSmooth.cxx
@@ -18,12 +18,11 @@
 *                                                                             *
 ******************************************************************************/
 
-
-#include "Riostream.h"
 #include "TMath.h"
 #include "TGraphSmooth.h"
 #include "TGraphErrors.h"
 
+#include <iostream>
 
 //______________________________________________________________________
 /** \class TGraphSmooth
diff --git a/hist/hist/src/TH2Poly.cxx b/hist/hist/src/TH2Poly.cxx
index a9877bb9ccff3..f513cfb9e7038 100644
--- a/hist/hist/src/TH2Poly.cxx
+++ b/hist/hist/src/TH2Poly.cxx
@@ -13,8 +13,6 @@
 #include "TH2Poly.h"
 #include "TMultiGraph.h"
 #include "TGraph.h"
-#include "TInterpreter.h"
-#include "Riostream.h"
 #include "TList.h"
 #include "TMath.h"
 #include <cassert>
diff --git a/hist/hist/src/TLimit.cxx b/hist/hist/src/TLimit.cxx
index ea41191c3c8b8..cead30324016b 100644
--- a/hist/hist/src/TLimit.cxx
+++ b/hist/hist/src/TLimit.cxx
@@ -92,8 +92,8 @@
 #include "TIterator.h"
 #include "TObjString.h"
 #include "TClassTable.h"
-#include "Riostream.h"
 
+#include <iostream>
 
 TArrayD *TLimit::fgTable = new TArrayD(0);
 TOrdCollection *TLimit::fgSystNames = new TOrdCollection();
diff --git a/hist/hist/src/TMultiDimFit.cxx b/hist/hist/src/TMultiDimFit.cxx
index 736fd55ed8a90..f4132ee144ec9 100644
--- a/hist/hist/src/TMultiDimFit.cxx
+++ b/hist/hist/src/TMultiDimFit.cxx
@@ -385,8 +385,6 @@
 [9]: classTMultiDimFit.html#eq:dS2
 */
 
-
-#include "Riostream.h"
 #include "TMultiDimFit.h"
 #include "TMath.h"
 #include "TH1.h"
@@ -397,6 +395,9 @@
 #include "TDecompChol.h"
 #include "TDatime.h"
 
+#include <fstream>
+#include <iostream>
+#include <iomanip>
 
 #define RADDEG (180. / TMath::Pi())
 #define DEGRAD (TMath::Pi() / 180.)
diff --git a/hist/hist/src/TPolyMarker.cxx b/hist/hist/src/TPolyMarker.cxx
index b28e63a910600..93cc806d0d476 100644
--- a/hist/hist/src/TPolyMarker.cxx
+++ b/hist/hist/src/TPolyMarker.cxx
@@ -9,7 +9,6 @@
  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
  *************************************************************************/
 
-#include "Riostream.h"
 #include "TROOT.h"
 #include "TBuffer.h"
 #include "TVirtualPad.h"
@@ -17,7 +16,6 @@
 #include "TMath.h"
 
 
-
 /** \class TPolyMarker
     \ingroup Graphs
 A PolyMarker is defined by an array on N points in a 2-D space.
diff --git a/hist/hist/src/TPrincipal.cxx b/hist/hist/src/TPrincipal.cxx
index 38d3c3d5a5239..a5f32736a4b26 100644
--- a/hist/hist/src/TPrincipal.cxx
+++ b/hist/hist/src/TPrincipal.cxx
@@ -218,9 +218,10 @@ Christian Holm August 2000, CERN
 #include "TDatime.h"
 #include "TBrowser.h"
 #include "TROOT.h"
-#include "Riostream.h"
-
 
+#include <fstream>
+#include <iostream>
+#include <iomanip>
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Empty constructor. Do not use.
diff --git a/io/io/src/TStreamerInfo.cxx b/io/io/src/TStreamerInfo.cxx
index ba7f6ae80eb65..8f128d3e75883 100644
--- a/io/io/src/TStreamerInfo.cxx
+++ b/io/io/src/TStreamerInfo.cxx
@@ -4243,10 +4243,18 @@ UInt_t TStreamerInfo::GenerateIncludes(FILE *fp, char *inclist, const TList *ext
       if (ltype < lt) ltype = lt;
       if (ldata < ld) ldata = ld;
 
-      //must include Riostream.h in case of an STL container
+      //must include streaming classes in case of an STL container
       if (!incRiostream && element->InheritsFrom(TStreamerSTL::Class())) {
          incRiostream = kTRUE;
-         TMakeProject::AddInclude( fp, "Riostream.h", kFALSE, inclist);
+#ifdef __APPLE__
+         // Workaround for https://github.com/llvm/llvm-project/issues/138683
+         // Include <chrono> before <fstream> to ensure _FilesystemClock is defined
+         // Can be removed once the upstream issue is fixed.
+         TMakeProject::AddInclude( fp, "chrono", kTRUE, inclist);
+#endif
+         TMakeProject::AddInclude( fp, "fstream", kTRUE, inclist);
+         TMakeProject::AddInclude( fp, "iostream", kTRUE, inclist);
+         TMakeProject::AddInclude( fp, "iomanip", kTRUE, inclist);
       }
 
       //get include file name if any
diff --git a/math/smatrix/test/kalman.C b/math/smatrix/test/kalman.C
index ee03823c33ba3..dacdd246ec112 100644
--- a/math/smatrix/test/kalman.C
+++ b/math/smatrix/test/kalman.C
@@ -1,4 +1,3 @@
-#include "Riostream.h"
 #include "TFile.h"
 #include "TCanvas.h"
 #include "TSystem.h"
diff --git a/net/net/src/TGridJDL.cxx b/net/net/src/TGridJDL.cxx
index 5ba80ec545a31..7010992c6b697 100644
--- a/net/net/src/TGridJDL.cxx
+++ b/net/net/src/TGridJDL.cxx
@@ -12,9 +12,6 @@
 
 #include "TGridJDL.h"
 #include "TObjString.h"
-#include "Riostream.h"
-
-
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Cleanup.
diff --git a/net/net/src/TSQLColumnInfo.cxx b/net/net/src/TSQLColumnInfo.cxx
index 0af063d996406..66431ec184d7f 100644
--- a/net/net/src/TSQLColumnInfo.cxx
+++ b/net/net/src/TSQLColumnInfo.cxx
@@ -40,8 +40,8 @@
 #include "TSQLColumnInfo.h"
 #include "TSQLServer.h"
 #include "TROOT.h"
-#include "Riostream.h"
 
+#include <iostream>
 
 ////////////////////////////////////////////////////////////////////////////////
 /// default contructor
diff --git a/net/net/src/TSQLTableInfo.cxx b/net/net/src/TSQLTableInfo.cxx
index 1be6678ecd51d..4ed246dada675 100644
--- a/net/net/src/TSQLTableInfo.cxx
+++ b/net/net/src/TSQLTableInfo.cxx
@@ -19,15 +19,13 @@
 //
 ////////////////////////////////////////////////////////////////////////////////
 
-
-
 #include "TSQLTableInfo.h"
 
 #include "TSQLColumnInfo.h"
 #include "TList.h"
 #include "TROOT.h"
-#include "Riostream.h"
 
+#include <iostream>
 
 ////////////////////////////////////////////////////////////////////////////////
 /// default constructor
diff --git a/tmva/tmva/test/stressTMVA.cxx b/tmva/tmva/test/stressTMVA.cxx
index 8ed7da829cb88..ebb030491250f 100644
--- a/tmva/tmva/test/stressTMVA.cxx
+++ b/tmva/tmva/test/stressTMVA.cxx
@@ -2771,7 +2771,6 @@ bool MethodUnitTestWithComplexData::create_data(const char *filename, int nmax)
 // Authors: Christoph Rosemann, Eckhard von Toerne   July 2010
 // TMVA unit tests
 
-#include "Riostream.h"
 #include "TSystem.h"
 #include "TROOT.h"
 #include "TBenchmark.h"