diff --git a/samples/f90/README.rst b/samples/f90/README.rst
index 90db49663..1c7bbf9ff 100644
--- a/samples/f90/README.rst
+++ b/samples/f90/README.rst
@@ -2,3 +2,7 @@ Fortran Examples
 ================
 
 Examples for both Fortran 77 and Fortran 90.
+
+.. caution::
+    The Fortran interface is an experimental part of the Cantera API and may be changed
+    or removed without notice.
diff --git a/src/fortran/cantera.f90 b/src/fortran/cantera.f90
index dbf066422..aa8206cb6 100644
--- a/src/fortran/cantera.f90
+++ b/src/fortran/cantera.f90
@@ -2,6 +2,9 @@
 ! an application program. It's primary purpose is to provide generic
 ! procedure names that map to specific procedures depending on the
 ! argument types.
+!
+! @warning  The Fortran API is an experimental part of %Cantera and
+!   may be changed or removed without notice.
 
 ! This file is part of Cantera. See License.txt in the top-level directory or
 ! at https://cantera.org/license.txt for license and copyright information.
diff --git a/src/fortran/cantera_funcs.f90 b/src/fortran/cantera_funcs.f90
index 5b0d1b897..db99dde9d 100644
--- a/src/fortran/cantera_funcs.f90
+++ b/src/fortran/cantera_funcs.f90
@@ -1,6 +1,9 @@
 ! This file is part of Cantera. See License.txt in the top-level directory or
 ! at https://cantera.org/license.txt for license and copyright information.
 
+! @warning  The Fortran API is an experimental part of %Cantera and
+!   may be changed or removed without notice.
+
 module cantera_funcs
 
   use cantera_thermo
diff --git a/src/fortran/cantera_kinetics.f90 b/src/fortran/cantera_kinetics.f90
index d08c5b02b..d7ffda90f 100644
--- a/src/fortran/cantera_kinetics.f90
+++ b/src/fortran/cantera_kinetics.f90
@@ -1,6 +1,9 @@
 ! This file is part of Cantera. See License.txt in the top-level directory or
 ! at https://cantera.org/license.txt for license and copyright information.
 
+! @warning  The Fortran API is an experimental part of %Cantera and
+!   may be changed or removed without notice.
+
 module cantera_kinetics
 
   use cantera_thermo
diff --git a/src/fortran/cantera_thermo.f90 b/src/fortran/cantera_thermo.f90
index 53f4d61c5..bab835454 100644
--- a/src/fortran/cantera_thermo.f90
+++ b/src/fortran/cantera_thermo.f90
@@ -1,6 +1,9 @@
 ! This file is part of Cantera. See License.txt in the top-level directory or
 ! at https://cantera.org/license.txt for license and copyright information.
 
+! @warning  The Fortran API is an experimental part of %Cantera and
+!   may be changed or removed without notice.
+
 module cantera_thermo
 
   use fct
diff --git a/src/fortran/cantera_transport.f90 b/src/fortran/cantera_transport.f90
index ef246c46c..7baf4f475 100644
--- a/src/fortran/cantera_transport.f90
+++ b/src/fortran/cantera_transport.f90
@@ -1,6 +1,9 @@
 ! This file is part of Cantera. See License.txt in the top-level directory or
 ! at https://cantera.org/license.txt for license and copyright information.
 
+! @warning  The Fortran API is an experimental part of %Cantera and
+!   may be changed or removed without notice.
+
 module cantera_transport
 
   use cantera_thermo
diff --git a/src/fortran/fct.cpp b/src/fortran/fct.cpp
index 2d9da97f1..42340da3d 100644
--- a/src/fortran/fct.cpp
+++ b/src/fortran/fct.cpp
@@ -5,6 +5,9 @@
  *   library functions is provided that are declared "extern C". All
  *   Cantera objects are stored and referenced by integers - no
  *   pointers are passed to or from the calling application.
+ *
+ *   @warning  The Fortran API is an experimental part of %Cantera and
+ *      may be changed or removed without notice.
  */
 
 // This file is part of Cantera. See License.txt in the top-level directory or
diff --git a/src/fortran/fct_interface.f90 b/src/fortran/fct_interface.f90
index 474d9160c..18b0c5cfd 100644
--- a/src/fortran/fct_interface.f90
+++ b/src/fortran/fct_interface.f90
@@ -1,6 +1,9 @@
 ! This file is part of Cantera. See License.txt in the top-level directory or
 ! at https://cantera.org/license.txt for license and copyright information.
 
+! @warning  The Fortran API is an experimental part of %Cantera and
+!   may be changed or removed without notice.
+
 module fct
 interface