diff --git a/libgfortran/acinclude.m4 b/libgfortran/acinclude.m4
index a73207e5465..23fd621e518 100644
--- a/libgfortran/acinclude.m4
+++ b/libgfortran/acinclude.m4
@@ -274,6 +274,10 @@ AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [
   AC_CACHE_CHECK([whether we have a usable _Float128 type],
                  libgfor_cv_have_float128, [
    GCC_TRY_COMPILE_OR_LINK([
+    #ifdef __loongarch__
+    #error On LoongArch we should use long double instead; __float128 is only for porting existing code easier.
+    #endif
+
     _Float128 foo (_Float128 x)
     {
      _Complex _Float128 z1, z2;
diff --git a/libgfortran/configure b/libgfortran/configure
index 11a1bc5f070..9898a94a372 100755
--- a/libgfortran/configure
+++ b/libgfortran/configure
@@ -30283,6 +30283,10 @@ else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+    #ifdef __loongarch__
+    #error On LoongArch we should use long double instead; __float128 is only for porting existing code easier.
+    #endif
+
     _Float128 foo (_Float128 x)
     {
      _Complex _Float128 z1, z2;
@@ -30336,6 +30340,10 @@ fi
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+    #ifdef __loongarch__
+    #error On LoongArch we should use long double instead; __float128 is only for porting existing code easier.
+    #endif
+
     _Float128 foo (_Float128 x)
     {
      _Complex _Float128 z1, z2;
diff --git a/libquadmath/configure b/libquadmath/configure
index 49d70809218..f82dd3d0d6d 100755
--- a/libquadmath/configure
+++ b/libquadmath/configure
@@ -12843,6 +12843,10 @@ else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+    #ifdef __loongarch__
+    #error  On LoongArch we should use long double instead; __float128 is only for porting existing code easier.
+    #endif
+
     #if (!defined(_ARCH_PPC)) || defined(__LONG_DOUBLE_IEEE128__)
     typedef _Complex float __attribute__((mode(TC))) __complex128;
     #else
@@ -12894,6 +12898,10 @@ fi
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+    #ifdef __loongarch__
+    #error  On LoongArch we should use long double instead; __float128 is only for porting existing code easier.
+    #endif
+
     #if (!defined(_ARCH_PPC)) || defined(__LONG_DOUBLE_IEEE128__)
     typedef _Complex float __attribute__((mode(TC))) __complex128;
     #else
diff --git a/libquadmath/configure.ac b/libquadmath/configure.ac
index 349be2607c6..c64a8489219 100644
--- a/libquadmath/configure.ac
+++ b/libquadmath/configure.ac
@@ -233,6 +233,10 @@ AM_CONDITIONAL(LIBQUAD_USE_SYMVER_SUN, [test "x$quadmath_use_symver" = xsun])
 
 AC_CACHE_CHECK([whether __float128 is supported], [libquad_cv_have_float128],
   [GCC_TRY_COMPILE_OR_LINK([
+    #ifdef __loongarch__
+    #error  On LoongArch we should use long double instead; __float128 is only for porting existing code easier.
+    #endif
+
     #if (!defined(_ARCH_PPC)) || defined(__LONG_DOUBLE_IEEE128__)
     typedef _Complex float __attribute__((mode(TC))) __complex128;
     #else