diff --git a/README/ReleaseNotes/v640/index.md b/README/ReleaseNotes/v640/index.md
index e4bd1f13fd9b9..0c3898e06232e 100644
--- a/README/ReleaseNotes/v640/index.md
+++ b/README/ReleaseNotes/v640/index.md
@@ -64,6 +64,7 @@ The following people have contributed to this new version:
   The Davix I/O code in ROOT remains uneffected and is built as before provided that the Davix library is found on the system.
 * `RRealField::SetQuantized` now has a new overload and the existing signature has been deprecated. The new overload enforces proper ordering of the arguments.
   The deprecated overload will be removed in ROOT 6.42.
+* The bindings to the R programming language that are enabled with the `r=ON` build option (`TRInterface` and friends) are deprecated and will be removed in ROOT 6.42. Their maintenance is no longer justified, given the broader adoption of the scientific Python ecosystem. Users who still rely on R from C++ are encouraged to call R directly via https://cran.r-project.org/package=RInside, which is what the ROOT bindings were using internally.
 
 ## Removals
 
diff --git a/cmake/modules/RootBuildOptions.cmake b/cmake/modules/RootBuildOptions.cmake
index 7562c6118c30e..a69d9cc1040ea 100644
--- a/cmake/modules/RootBuildOptions.cmake
+++ b/cmake/modules/RootBuildOptions.cmake
@@ -383,7 +383,7 @@ foreach(opt afdsmgrd afs alien bonjour builtin_afterimage builtin_davix castor c
 endforeach()
 
 #---Deprecated options------------------------------------------------------------------------
-foreach(opt builtin_cppzmq builtin_zeromq)
+foreach(opt builtin_cppzmq builtin_zeromq r)
   if(${opt})
     message(DEPRECATION ">>> Option '${opt}' is deprecated and will be removed in the next release of ROOT. Please contact root-dev@cern.ch should you still need it.")
   endif()