diff --git a/Cabal-syntax/src/Distribution/System.hs b/Cabal-syntax/src/Distribution/System.hs
index 5142bf523b1..730bb6d685e 100644
--- a/Cabal-syntax/src/Distribution/System.hs
+++ b/Cabal-syntax/src/Distribution/System.hs
@@ -112,6 +112,7 @@ data OS
   | Android -- mobile OSs
   | Ghcjs
   | Wasi
+  | Haiku
   | OtherOS String
   deriving (Eq, Generic, Ord, Show, Read, Typeable, Data)
 
@@ -138,6 +139,7 @@ knownOSs =
   , Android
   , Ghcjs
   , Wasi
+  , Haiku
   ]
 
 osAliases :: ClassificationStrictness -> OS -> [String]
diff --git a/Cabal-tests/tests/UnitTests/Distribution/Utils/Structured.hs b/Cabal-tests/tests/UnitTests/Distribution/Utils/Structured.hs
index 37d38f2bac4..a396dea860c 100644
--- a/Cabal-tests/tests/UnitTests/Distribution/Utils/Structured.hs
+++ b/Cabal-tests/tests/UnitTests/Distribution/Utils/Structured.hs
@@ -27,9 +27,9 @@ tests = testGroup "Distribution.Utils.Structured"
     -- The difference is in encoding of newtypes
 #if MIN_VERSION_base(4,7,0)
     , testCase "GenericPackageDescription" $
-      md5Check (Proxy :: Proxy GenericPackageDescription) 0x8d8f340f10a58b8d8a87bf42213dac89
+      md5Check (Proxy :: Proxy GenericPackageDescription) 0xc7d1064aaf2c9bcf92c3d7f23e6d7e94
     , testCase "LocalBuildInfo" $
-      md5Check (Proxy :: Proxy LocalBuildInfo) 0xbb22c3258d3092f31e992bc093d09170
+      md5Check (Proxy :: Proxy LocalBuildInfo) 0x0324f420f9fb98417098127a414cc7c0
 #endif
     ]
 
diff --git a/Cabal/src/Distribution/Simple/GHC.hs b/Cabal/src/Distribution/Simple/GHC.hs
index 892526e399f..8949b24c9cf 100644
--- a/Cabal/src/Distribution/Simple/GHC.hs
+++ b/Cabal/src/Distribution/Simple/GHC.hs
@@ -2258,6 +2258,7 @@ getRPaths lbi clbi | supportRPaths hostOS = do
     supportRPaths Ghcjs = False
     supportRPaths Wasi = False
     supportRPaths Hurd = False
+    supportRPaths Haiku = False
     supportRPaths (OtherOS _) = False
 -- Do _not_ add a default case so that we get a warning here when a new OS
 -- is added.
diff --git a/Cabal/src/Distribution/Simple/GHCJS.hs b/Cabal/src/Distribution/Simple/GHCJS.hs
index 8515635de54..6c9bf34f0eb 100644
--- a/Cabal/src/Distribution/Simple/GHCJS.hs
+++ b/Cabal/src/Distribution/Simple/GHCJS.hs
@@ -1794,6 +1794,7 @@ getRPaths lbi clbi | supportRPaths hostOS = do
     supportRPaths Ghcjs = False
     supportRPaths Wasi = False
     supportRPaths Hurd = False
+    supportRPaths Haiku = False
     supportRPaths (OtherOS _) = False
 -- Do _not_ add a default case so that we get a warning here when a new OS
 -- is added.
diff --git a/Cabal/src/Distribution/Simple/InstallDirs.hs b/Cabal/src/Distribution/Simple/InstallDirs.hs
index c77ee8a99b2..eead40c597b 100644
--- a/Cabal/src/Distribution/Simple/InstallDirs.hs
+++ b/Cabal/src/Distribution/Simple/InstallDirs.hs
@@ -204,6 +204,7 @@ defaultInstallDirs' False comp userInstall _hasLibs = do
         Windows -> do
           windowsProgramFilesDir <- getWindowsProgramFilesDir
           return (windowsProgramFilesDir </> "Haskell")
+        Haiku -> return "/boot/system/non-packaged"
         _ -> return "/usr/local"
   installLibDir <-
     case buildOS of
@@ -226,17 +227,27 @@ defaultInstallDirs' False comp userInstall _hasLibs = do
         , flibdir = "$libdir"
         , libexecdir = case buildOS of
             Windows -> "$prefix" </> "$libname"
+            Haiku -> "$libdir"
             _other -> "$prefix" </> "libexec"
-        , includedir = "$libdir" </> "$libsubdir" </> "include"
+        , includedir = case buildOS of
+            Haiku -> "$prefix" </> "develop" </> "headers"
+            _other -> "$libdir" </> "$libsubdir" </> "include"
         , datadir = case buildOS of
             Windows -> "$prefix"
+            Haiku -> "$prefix" </> "data"
             _other -> "$prefix" </> "share"
         , datasubdir = "$abi" </> "$pkgid"
-        , docdir = "$datadir" </> "doc" </> "$abi" </> "$pkgid"
-        , mandir = "$datadir" </> "man"
+        , docdir = case buildOS of
+            Haiku -> "$prefix" </> "documentation"
+            _other -> "$datadir" </> "doc" </> "$abi" </> "$pkgid"
+        , mandir = case buildOS of
+            Haiku -> "$docdir" </> "man"
+            _other -> "$datadir" </> "man"
         , htmldir = "$docdir" </> "html"
         , haddockdir = "$htmldir"
-        , sysconfdir = "$prefix" </> "etc"
+        , sysconfdir = case buildOS of
+            Haiku -> "boot" </> "system" </> "settings"
+            _other -> "$prefix" </> "etc"
         }
 
 -- ---------------------------------------------------------------------------
diff --git a/Cabal/src/Distribution/Simple/PreProcess.hs b/Cabal/src/Distribution/Simple/PreProcess.hs
index 5531140629f..6321a63b03b 100644
--- a/Cabal/src/Distribution/Simple/PreProcess.hs
+++ b/Cabal/src/Distribution/Simple/PreProcess.hs
@@ -848,6 +848,7 @@ platformDefines lbi =
       Ghcjs -> ["ghcjs"]
       Wasi -> ["wasi"]
       Hurd -> ["hurd"]
+      Haiku -> ["haiku"]
       OtherOS _ -> []
     archStr = case hostArch of
       I386 -> ["i386"]
diff --git a/changelog.d/pr-9006 b/changelog.d/pr-9006
new file mode 100644
index 00000000000..905a962e646
--- /dev/null
+++ b/changelog.d/pr-9006
@@ -0,0 +1,10 @@
+synopsis: Add Haiku as a known platform
+packages: Cabal
+prs: #9006
+
+description: {
+
+- Cabal: Distribution now recognises Haiku as a valid platform,
+  and also implements Haiku's unique directory layout.
+
+}