diff --git a/build.rs b/build.rs
index c4982111e..1ad245a64 100644
--- a/build.rs
+++ b/build.rs
@@ -24,6 +24,9 @@ fn main() {
     //
     // On CI, we detect the actual FreeBSD version and match its ABI exactly,
     // running tests to ensure that the ABI is correct.
+    //
+    // RISC-V first appeared in FreeBSD 12 so lacks FreeBSD 11's syscalls.
+    let arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
     match which_freebsd() {
         Some(10) if libc_ci || rustc_dep_of_std => {
             println!("cargo:rustc-cfg=freebsd10")
@@ -31,7 +34,13 @@ fn main() {
         Some(11) if libc_ci => println!("cargo:rustc-cfg=freebsd11"),
         Some(12) if libc_ci => println!("cargo:rustc-cfg=freebsd12"),
         Some(13) if libc_ci => println!("cargo:rustc-cfg=freebsd13"),
-        Some(_) | None => println!("cargo:rustc-cfg=freebsd11"),
+        Some(_) | None => {
+            if arch == "riscv64" {
+                println!("cargo:rustc-cfg=freebsd12")
+            } else {
+                println!("cargo:rustc-cfg=freebsd11")
+            }
+        }
     }
 
     // On CI: deny all warnings
diff --git a/src/unix/bsd/freebsdlike/freebsd/freebsd11/mod.rs b/src/unix/bsd/freebsdlike/freebsd/freebsd11/mod.rs
index a0b510514..e3c06c634 100644
--- a/src/unix/bsd/freebsdlike/freebsd/freebsd11/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/freebsd11/mod.rs
@@ -217,7 +217,8 @@ extern "C" {
 
 cfg_if! {
     if #[cfg(any(target_arch = "x86_64",
-                 target_arch = "aarch64"))] {
+                 target_arch = "aarch64",
+                 target_arch = "riscv64"))] {
         mod b64;
         pub use self::b64::*;
     }
diff --git a/src/unix/bsd/freebsdlike/freebsd/freebsd12/mod.rs b/src/unix/bsd/freebsdlike/freebsd/freebsd12/mod.rs
index 05cadd1de..ae79db3f9 100644
--- a/src/unix/bsd/freebsdlike/freebsd/freebsd12/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/freebsd12/mod.rs
@@ -241,7 +241,8 @@ extern "C" {
 
 cfg_if! {
     if #[cfg(any(target_arch = "x86_64",
-                 target_arch = "aarch64"))] {
+                 target_arch = "aarch64",
+                 target_arch = "riscv64"))] {
         mod b64;
         pub use self::b64::*;
     }
diff --git a/src/unix/bsd/freebsdlike/freebsd/freebsd13/mod.rs b/src/unix/bsd/freebsdlike/freebsd/freebsd13/mod.rs
index 93ef2a2ad..c270ca09b 100644
--- a/src/unix/bsd/freebsdlike/freebsd/freebsd13/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/freebsd13/mod.rs
@@ -271,7 +271,8 @@ extern "C" {
 
 cfg_if! {
     if #[cfg(any(target_arch = "x86_64",
-                 target_arch = "aarch64"))] {
+                 target_arch = "aarch64",
+                 target_arch = "riscv64"))] {
         mod b64;
         pub use self::b64::*;
     }
diff --git a/src/unix/bsd/freebsdlike/freebsd/mod.rs b/src/unix/bsd/freebsdlike/freebsd/mod.rs
index 99a7f2dc3..73b09d989 100644
--- a/src/unix/bsd/freebsdlike/freebsd/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/mod.rs
@@ -1971,6 +1971,9 @@ cfg_if! {
     } else if #[cfg(target_arch = "powerpc")] {
         mod powerpc;
         pub use self::powerpc::*;
+    } else if #[cfg(target_arch = "riscv64")] {
+        mod riscv64;
+        pub use self::riscv64::*;
     } else {
         // Unknown target_arch
     }
diff --git a/src/unix/bsd/freebsdlike/freebsd/riscv64.rs b/src/unix/bsd/freebsdlike/freebsd/riscv64.rs
new file mode 100644
index 000000000..822e3ff48
--- /dev/null
+++ b/src/unix/bsd/freebsdlike/freebsd/riscv64.rs
@@ -0,0 +1,154 @@
+pub type c_char = u8;
+pub type c_long = i64;
+pub type c_ulong = u64;
+pub type wchar_t = i32;
+pub type time_t = i64;
+pub type suseconds_t = i64;
+pub type register_t = i64;
+
+// should be pub(crate), but that requires Rust 1.18.0
+cfg_if! {
+    if #[cfg(libc_const_size_of)] {
+        #[doc(hidden)]
+        pub const _ALIGNBYTES: usize = ::mem::size_of::<::c_long>() - 1;
+    } else {
+        #[doc(hidden)]
+        pub const _ALIGNBYTES: usize = 8 - 1;
+    }
+}
+
+s_no_extra_traits! {
+    pub struct gpregs {
+        pub gp_ra: ::register_t,
+        pub gp_sp: ::register_t,
+        pub gp_gp: ::register_t,
+        pub gp_tp: ::register_t,
+        pub gp_t: [::register_t; 7],
+        pub gp_s: [::register_t; 12],
+        pub gp_a: [::register_t; 8],
+        pub gp_sepc: ::register_t,
+        pub gp_sstatus: ::register_t,
+    }
+
+    pub struct fpregs {
+        pub fp_x: [[::register_t; 2]; 32],
+        pub fp_fcsr: ::register_t,
+        pub fp_flags: ::c_int,
+        pub fp_pad: ::c_int,
+    }
+
+    pub struct mcontext_t {
+        pub mc_gpregs: gpregs,
+        pub mc_fpregs: fpregs,
+        pub mc_flags: ::c_int,
+        pub mc_pad: ::c_int,
+        pub mc_spare: [u64; 8],
+    }
+}
+
+cfg_if! {
+    if #[cfg(feature = "extra_traits")] {
+        impl PartialEq for gpregs {
+            fn eq(&self, other: &gpregs) -> bool {
+                self.gp_ra == other.gp_ra &&
+                self.gp_sp == other.gp_sp &&
+                self.gp_gp == other.gp_gp &&
+                self.gp_tp == other.gp_tp &&
+                self.gp_t.iter().zip(other.gp_t.iter()).all(|(a, b)| a == b) &&
+                self.gp_s.iter().zip(other.gp_s.iter()).all(|(a, b)| a == b) &&
+                self.gp_a.iter().zip(other.gp_a.iter()).all(|(a, b)| a == b) &&
+                self.gp_sepc == other.gp_sepc &&
+                self.gp_sstatus == other.gp_sstatus
+            }
+        }
+        impl Eq for gpregs {}
+        impl ::fmt::Debug for gpregs {
+            fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result {
+                f.debug_struct("gpregs")
+                    .field("gp_ra", &self.gp_ra)
+                    .field("gp_sp", &self.gp_sp)
+                    .field("gp_gp", &self.gp_gp)
+                    .field("gp_tp", &self.gp_tp)
+                    .field("gp_t", &self.gp_t)
+                    .field("gp_s", &self.gp_s)
+                    .field("gp_a", &self.gp_a)
+                    .field("gp_sepc", &self.gp_sepc)
+                    .field("gp_sstatus", &self.gp_sstatus)
+                    .finish()
+            }
+        }
+        impl ::hash::Hash for gpregs {
+            fn hash<H: ::hash::Hasher>(&self, state: &mut H) {
+                self.gp_ra.hash(state);
+                self.gp_sp.hash(state);
+                self.gp_gp.hash(state);
+                self.gp_tp.hash(state);
+                self.gp_t.hash(state);
+                self.gp_s.hash(state);
+                self.gp_a.hash(state);
+                self.gp_sepc.hash(state);
+                self.gp_sstatus.hash(state);
+            }
+        }
+        impl PartialEq for fpregs {
+            fn eq(&self, other: &fpregs) -> bool {
+                self.fp_x == other.fp_x &&
+                self.fp_fcsr == other.fp_fcsr &&
+                self.fp_flags == other.fp_flags &&
+                self.fp_pad == other.fp_pad
+            }
+        }
+        impl Eq for fpregs {}
+        impl ::fmt::Debug for fpregs {
+            fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result {
+                f.debug_struct("fpregs")
+                    .field("fp_x", &self.fp_x)
+                    .field("fp_fcsr", &self.fp_fcsr)
+                    .field("fp_flags", &self.fp_flags)
+                    .field("fp_pad", &self.fp_pad)
+                    .finish()
+            }
+        }
+        impl ::hash::Hash for fpregs {
+            fn hash<H: ::hash::Hasher>(&self, state: &mut H) {
+                self.fp_x.hash(state);
+                self.fp_fcsr.hash(state);
+                self.fp_flags.hash(state);
+                self.fp_pad.hash(state);
+            }
+        }
+        impl PartialEq for mcontext_t {
+            fn eq(&self, other: &mcontext_t) -> bool {
+                self.mc_gpregs == other.mc_gpregs &&
+                self.mc_fpregs == other.mc_fpregs &&
+                self.mc_flags == other.mc_flags &&
+                self.mc_pad == other.mc_pad &&
+                self.mc_spare.iter().zip(other.mc_spare.iter()).all(|(a, b)| a == b)
+            }
+        }
+        impl Eq for mcontext_t {}
+        impl ::fmt::Debug for mcontext_t {
+            fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result {
+                f.debug_struct("mcontext_t")
+                    .field("mc_gpregs", &self.mc_gpregs)
+                    .field("mc_fpregs", &self.mc_fpregs)
+                    .field("mc_flags", &self.mc_flags)
+                    .field("mc_pad", &self.mc_pad)
+                    .field("mc_spare", &self.mc_spare)
+                    .finish()
+            }
+        }
+        impl ::hash::Hash for mcontext_t {
+            fn hash<H: ::hash::Hasher>(&self, state: &mut H) {
+                self.mc_gpregs.hash(state);
+                self.mc_fpregs.hash(state);
+                self.mc_flags.hash(state);
+                self.mc_pad.hash(state);
+                self.mc_spare.hash(state);
+            }
+        }
+    }
+}
+
+pub const MAP_32BIT: ::c_int = 0x00080000;
+pub const MINSIGSTKSZ: ::size_t = 4096; // 1024 * 4