diff --git a/icu4c/source/common/putilimp.h b/icu4c/source/common/putilimp.h
index 6fe02ff8d289..8a8ff5008118 100644
--- a/icu4c/source/common/putilimp.h
+++ b/icu4c/source/common/putilimp.h
@@ -90,6 +90,8 @@ typedef size_t uintptr_t;
 #   define U_NL_LANGINFO_CODESET -1
 #elif U_PLATFORM == U_PF_OS400
    /* not defined */
+#elif U_PLATFORM == U_PF_HAIKU
+   /* not defined */
 #else
 #   define U_NL_LANGINFO_CODESET CODESET
 #endif
@@ -103,6 +105,8 @@ typedef size_t uintptr_t;
 #endif
 #elif U_PLATFORM == U_PF_OS400
    /* not defined */
+#elif U_PLATFORM == U_PF_HAIKU
+   /* not defined */
 #else
 #   define U_TZSET tzset
 #endif
@@ -141,6 +145,8 @@ typedef size_t uintptr_t;
 #endif
 #elif U_PLATFORM == U_PF_OS400
    /* not defined */
+#elif U_PLATFORM == U_PF_HAIKU
+    /* not defined, (well it is but a loop back to icu) */
 #else
 #   define U_TZNAME tzname
 #endif
diff --git a/icu4c/source/common/unicode/platform.h b/icu4c/source/common/unicode/platform.h
index 309ad8bb1fe3..b2fcb21ef130 100644
--- a/icu4c/source/common/unicode/platform.h
+++ b/icu4c/source/common/unicode/platform.h
@@ -132,6 +132,8 @@
 #define U_PF_BROWSER_NATIVE_CLIENT 4020
 /** Android is based on Linux. @internal */
 #define U_PF_ANDROID 4050
+/** Haiku is a POSIX-ish platform. @internal */
+#define U_PF_HAIKU 4080
 /** Fuchsia is a POSIX-ish platform. @internal */
 #define U_PF_FUCHSIA 4100
 /* Maximum value for Linux-based platform is 4499 */
@@ -202,6 +204,8 @@
 #   define U_PLATFORM U_PF_OS390
 #elif defined(__OS400__) || defined(__TOS_OS400__)
 #   define U_PLATFORM U_PF_OS400
+#elif defined(__HAIKU__)
+#   define U_PLATFORM U_PF_HAIKU
 #elif defined(__EMSCRIPTEN__)
 #   define U_PLATFORM U_PF_EMSCRIPTEN
 #else
diff --git a/icu4c/source/config/mh-haiku b/icu4c/source/config/mh-haiku
index bb814cdd426e..965c9495ab5f 100644
--- a/icu4c/source/config/mh-haiku
+++ b/icu4c/source/config/mh-haiku
@@ -20,7 +20,7 @@ LIBCPPFLAGS =
 THREADSCPPFLAGS =
 
 #
-CPPFLAGS += -D__STDC_ISO_10646__ -DU_CHARSET_IS_UTF8=1
+CPPFLAGS += -DU_CHARSET_IS_UTF8=1
 
 ## Compiler switch to embed a runtime search path
 LD_RPATH=
diff --git a/icu4c/source/configure.ac b/icu4c/source/configure.ac
index f663a76998cd..be1cca633065 100644
--- a/icu4c/source/configure.ac
+++ b/icu4c/source/configure.ac
@@ -306,7 +306,7 @@ if test "$ENABLE_STATIC" = "YES"; then
             OLD_LDFLAGS="${LDFLAGS}"
 
             case "${host}" in
-            *-linux*|i*86-*-*bsd*|i*86-pc-gnu)
+            *-linux*|i*86-*-*bsd*|i*86-pc-gnu|*-haiku*)
                 if test "$GCC" = yes; then
                     CPPFLAGS="${CPPFLAGS} -ffunction-sections -fdata-sections"
                     LDFLAGS="${LDFLAGS} -Wl,--gc-sections"
@@ -1191,6 +1191,7 @@ case "${host}" in
 	*-*-nto*)	platform=U_QNX ;;
 	*-dec-osf*) 	platform=U_OSF ;;
 	*-*-beos)		platform=U_BEOS ;;
+	*-*-haiku)	platform=U_HAIKU ;;
 	*-*-irix*)		platform=U_IRIX ;;
 	*-ncr-*)		platform=U_MPRAS ;;
 	*) 		platform=U_UNKNOWN_PLATFORM ;;