diff --git a/CHANGELOG.md b/CHANGELOG.md
index 71f298d1e89..e3782801d1c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,7 +3,7 @@
 ## Current develop
 
 ### Added (new features/APIs/variables/...)
-- [[PR634]](https://github.com/lanl/singularity-eos/pull/643) Fixed `find_package(singularity-eos)` failures when built without closure variant. The CMake config now automatically detects which components were built and only requires those that exist, enabling header-only usage without the compiled library.
+- [[PR643]](https://github.com/lanl/singularity-eos/pull/643) Fixed `find_package(singularity-eos)` failures when built without closure variant. The CMake config now automatically detects which components were built and only requires those that exist, enabling header-only usage without the compiled library.
 - [[PR632]](https://github.com/lanl/singularity-eos/pull/632) Added generic constructors to SpinerEOSDependsRhoSie and SpinerEOSDependsRhoT that build tables from any EOS object.
 - [[PR623]](https://github.com/lanl/singularity-eos/pull/623) Expanded the sesame2spiner syntax to support multiple material definitions in one input file.
 - [[PR618]](https://github.com/lanl/singularity-eos/pull/618) Add PTDerivativesFromPreferred for computing derivatives of a mixture  in a cell
@@ -21,6 +21,9 @@
 - [[PR629]](https://github.com/lanl/singularity-eos/pull/629) Use macros and eos_base and eos_variant to reduce boiler plate
 - [[PR626]](https://github.com/lanl/singularity-eos/pull/626) Fix C++20 warnings related to lambdas
 
+### Deprecated (soon to be removed behavior/API/variables/...)
+- [[PR644]](https://github.com/lanl/singularity-eos/pull/644) The Fortran interface has been deprecated and will be removed on the next release.
+
 ## Release 1.11.1
 Date: 03/25/2026
 
diff --git a/singularity-eos/eos/singularity_eos.f90 b/singularity-eos/eos/singularity_eos.f90
index e13e3d93eb0..a64de15e029 100644
--- a/singularity-eos/eos/singularity_eos.f90
+++ b/singularity-eos/eos/singularity_eos.f90
@@ -12,6 +12,21 @@
 ! publicly and display publicly, and to permit others to do so.
 !------------------------------------------------------------------------------
 
+#if defined(ALLOW_DEPRECATED)
+! Disable warnings if explicit override flag is passed
+#define DEPRECATED_MODULE
+
+#elif defined(__flang__) || defined(__GNUC__)
+#define DEPRECATED_MODULE __attribute__((deprecated("The singularity-eos module is deprecated.")))
+
+#elif defined(__INTEL_COMPILER)
+#define DEPRECATED_MODULE __declspec(deprecated)
+
+#else
+#define DEPRECATED_MODULE
+#endif
+
+
 module singularity_eos_types
   use, intrinsic :: iso_c_binding
   implicit none