diff --git a/lib/std/c/dragonfly.zig b/lib/std/c/dragonfly.zig
index c265fd0ff27f..8beba21fbb8f 100644
--- a/lib/std/c/dragonfly.zig
+++ b/lib/std/c/dragonfly.zig
@@ -22,6 +22,9 @@ pub extern "c" fn lwp_gettid() c_int;
 
 pub extern "c" fn posix_memalign(memptr: *?*anyopaque, alignment: usize, size: usize) c_int;
 
+pub extern "c" fn mlockall(flags: c_int) c_int;
+pub extern "c" fn munlockall() c_int;
+
 pub const pthread_attr_t = extern struct { // copied from freebsd
     __size: [56]u8,
     __align: c_long,
@@ -937,6 +940,11 @@ pub const MADV = struct {
     pub const SETMAP = 11;
 };
 
+pub const MCL = struct {
+    pub const CURRENT = 0x01;
+    pub const FUTURE = 0x02;
+};
+
 pub const LOCK = struct {
     pub const SH = 1;
     pub const EX = 2;
diff --git a/lib/std/c/freebsd.zig b/lib/std/c/freebsd.zig
index 6d0b88e3c35b..fec06c9111c0 100644
--- a/lib/std/c/freebsd.zig
+++ b/lib/std/c/freebsd.zig
@@ -25,6 +25,9 @@ pub extern "c" fn getpid() pid_t;
 
 pub extern "c" fn kinfo_getfile(pid: pid_t, cntp: *c_int) ?[*]kinfo_file;
 
+pub extern "c" fn mlockall(flags: c_int) c_int;
+pub extern "c" fn munlockall() c_int;
+
 pub const sf_hdtr = extern struct {
     headers: [*]const iovec_const,
     hdr_cnt: c_int,
@@ -606,6 +609,11 @@ pub const MADV = struct {
     pub const PROTECT = 10;
 };
 
+pub const MCL = struct {
+    pub const CURRENT = 0x01;
+    pub const FUTURE = 0x02;
+};
+
 pub const MSF = struct {
     pub const ASYNC = 1;
     pub const INVALIDATE = 2;
diff --git a/lib/std/c/linux.zig b/lib/std/c/linux.zig
index 1a3c63451502..60eebddff76a 100644
--- a/lib/std/c/linux.zig
+++ b/lib/std/c/linux.zig
@@ -23,6 +23,7 @@ pub const IOV_MAX = linux.IOV_MAX;
 pub const IPPROTO = linux.IPPROTO;
 pub const LOCK = linux.LOCK;
 pub const MADV = linux.MADV;
+pub const MCL = linux.MCL;
 pub const MSF = linux.MSF;
 pub const MMAP2_UNIT = linux.MMAP2_UNIT;
 pub const MSG = linux.MSG;
@@ -306,6 +307,9 @@ pub extern "c" fn madvise(
     advice: c_uint,
 ) c_int;
 
+pub extern "c" fn mlockall(flags: c_int) c_int;
+pub extern "c" fn munlockall() c_int;
+
 pub const pthread_attr_t = extern struct {
     __size: [56]u8,
     __align: c_long,
diff --git a/lib/std/c/netbsd.zig b/lib/std/c/netbsd.zig
index fb2aefdb44b2..7522e507bc51 100644
--- a/lib/std/c/netbsd.zig
+++ b/lib/std/c/netbsd.zig
@@ -26,6 +26,9 @@ pub const sigaltstack = __sigaltstack14;
 
 pub extern "c" fn posix_memalign(memptr: *?*anyopaque, alignment: usize, size: usize) c_int;
 
+pub extern "c" fn mlockall(flags: c_int) c_int;
+pub extern "c" fn munlockall() c_int;
+
 pub const pthread_spin_t = switch (builtin.cpu.arch) {
     .aarch64, .aarch64_be, .aarch64_32 => u8,
     .mips, .mipsel, .mips64, .mips64el => u32,
@@ -500,6 +503,11 @@ pub const CLOCK = struct {
     pub const PROCESS_CPUTIME_ID = 0x40000000;
 };
 
+pub const MCL = struct {
+    pub const CURRENT = 0x01;
+    pub const FUTURE = 0x02;
+};
+
 pub const MSF = struct {
     pub const ASYNC = 1;
     pub const INVALIDATE = 2;
diff --git a/lib/std/c/openbsd.zig b/lib/std/c/openbsd.zig
index e97798b0e794..03fc0f8c110e 100644
--- a/lib/std/c/openbsd.zig
+++ b/lib/std/c/openbsd.zig
@@ -19,6 +19,9 @@ pub extern "c" fn pipe2(fds: *[2]fd_t, flags: std.c.O) c_int;
 pub extern "c" fn getdents(fd: c_int, buf_ptr: [*]u8, nbytes: usize) c_int;
 pub extern "c" fn sigaltstack(ss: ?*stack_t, old_ss: ?*stack_t) c_int;
 
+pub extern "c" fn mlockall(flags: c_int) c_int;
+pub extern "c" fn munlockall() c_int;
+
 pub const pthread_spinlock_t = extern struct {
     inner: ?*anyopaque = null,
 };
@@ -425,6 +428,11 @@ pub const CLOCK = struct {
     pub const THREAD_CPUTIME_ID = 4;
 };
 
+pub const MCL = struct {
+    pub const CURRENT = 0x01;
+    pub const FUTURE = 0x02;
+};
+
 pub const MSF = struct {
     pub const ASYNC = 1;
     pub const INVALIDATE = 2;
diff --git a/lib/std/c/solaris.zig b/lib/std/c/solaris.zig
index 31900c83728b..2b2cf2544a80 100644
--- a/lib/std/c/solaris.zig
+++ b/lib/std/c/solaris.zig
@@ -20,6 +20,8 @@ pub extern "c" fn posix_memalign(memptr: *?*anyopaque, alignment: usize, size: u
 pub extern "c" fn sysconf(sc: c_int) i64;
 pub extern "c" fn signalfd(fd: fd_t, mask: *const sigset_t, flags: u32) c_int;
 pub extern "c" fn madvise(address: [*]u8, len: usize, advise: u32) c_int;
+pub extern "c" fn mlockall(flags: c_int) c_int;
+pub extern "c" fn munlockall() c_int;
 
 pub const pthread_attr_t = extern struct {
     mutexattr: ?*anyopaque = null,
@@ -525,6 +527,11 @@ pub const MADV = struct {
     pub const PURGE = 9;
 };
 
+pub const MCL = struct {
+    pub const CURRENT = 0x01;
+    pub const FUTURE = 0x02;
+};
+
 pub const W = struct {
     pub const EXITED = 0o001;
     pub const TRAPPED = 0o002;
diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index 9ff272a3328e..7e4042df7d3e 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -2093,6 +2093,14 @@ pub fn madvise(address: [*]u8, len: usize, advice: u32) usize {
     return syscall3(.madvise, @intFromPtr(address), len, advice);
 }
 
+pub fn mlockall(flags: i32) usize {
+    return syscall1(.mlockall, @as(usize, @bitCast(@as(isize, flags))));
+}
+
+pub fn munlockall() usize {
+    return syscall0(.munlockall);
+}
+
 pub fn pidfd_open(pid: pid_t, flags: u32) usize {
     return syscall2(.pidfd_open, @as(usize, @bitCast(@as(isize, pid))), flags);
 }
@@ -6051,6 +6059,16 @@ pub const MADV = struct {
     pub const SOFT_OFFLINE = 101;
 };
 
+pub const MCL = if (is_ppc or is_ppc64 or is_sparc) struct {
+    pub const CURRENT = 0x2000;
+    pub const FUTURE = 0x4000;
+    pub const ONFAULT = 0x8000;
+} else struct {
+    pub const CURRENT = 0x01;
+    pub const FUTURE = 0x02;
+    pub const ONFAULT = 0x04;
+};
+
 pub const POSIX_FADV = switch (native_arch) {
     .s390x => if (@typeInfo(usize).Int.bits == 64) struct {
         pub const NORMAL = 0;
diff --git a/lib/std/posix.zig b/lib/std/posix.zig
index fb2262e267bc..a03134735b2a 100644
--- a/lib/std/posix.zig
+++ b/lib/std/posix.zig
@@ -72,6 +72,7 @@ pub const Kevent = system.Kevent;
 pub const LOCK = system.LOCK;
 pub const MADV = system.MADV;
 pub const MAP = system.MAP;
+pub const MCL = system.MCL;
 pub const MSF = system.MSF;
 pub const MAX_ADDR_LEN = system.MAX_ADDR_LEN;
 pub const MFD = system.MFD;
@@ -7075,6 +7076,47 @@ pub fn madvise(ptr: [*]align(mem.page_size) u8, length: usize, advice: u32) Madv
     }
 }
 
+pub const MlockallError = error{
+    InvalidArgument,
+    LockedMemoryLimitExceeded,
+    NotImplemented,
+    PermissionDenied,
+    SystemResources,
+} || UnexpectedError;
+
+pub fn mlockall(flags: i32) MlockallError!void {
+    switch (native_os) {
+        .linux, .freebsd, .netbsd, .openbsd, .dragonfly, .solaris => {},
+        else => return error.NotImplemented,
+    }
+    switch (errno(system.mlockall(flags))) {
+        .SUCCESS => return,
+        .INVAL => return error.InvalidArgument,
+        .NOMEM => return error.LockedMemoryLimitExceeded,
+        .PERM => return error.PermissionDenied,
+        // Solaris and (Free|Net|Open)BSD, presumably no room to fault in locked stuff:
+        .AGAIN => return error.SystemResources,
+        else => |err| return unexpectedErrno(err),
+    }
+}
+
+pub const MunlockallError = error{
+    NotImplemented,
+    PermissionDenied,
+} || UnexpectedError;
+
+pub fn munlockall() MunlockallError!void {
+    switch (native_os) {
+        .linux, .freebsd, .netbsd, .openbsd, .dragonfly, .solaris => {},
+        else => return error.NotImplemented,
+    }
+    switch (errno(system.munlockall())) {
+        .SUCCESS => return,
+        .PERM => return error.PermissionDenied, // Solaris, possibly BSDs as well
+        else => |err| return unexpectedErrno(err),
+    }
+}
+
 pub const PerfEventOpenError = error{
     /// Returned if the perf_event_attr size value is too small (smaller
     /// than PERF_ATTR_SIZE_VER0), too big (larger than the page  size),
diff --git a/lib/std/posix/test.zig b/lib/std/posix/test.zig
index 1020bef4b7b0..5e07282e9b34 100644
--- a/lib/std/posix/test.zig
+++ b/lib/std/posix/test.zig
@@ -1315,3 +1315,22 @@ const CommonOpenFlags = packed struct {
         return result;
     }
 };
+
+test "mlockall/munlockall basic smoke" {
+    // We can't test a "real" mlockall because of various system perms/limits
+    // on locked memory and/or possible adverse effects on the testing
+    // environment itself. What we can do safely, I think, is execute
+    // mlockall() with a very-invalid (across all known platforms) flags value
+    // and expect E.INVAL (or NotImplemented when testing on non-supporting
+    // platforms), so that we at least exercise the code paths here.
+    const ok_errors = [_]anyerror{ error.NotImplemented, error.InvalidArgument };
+    try testing.expectErrors(&ok_errors, posix.mlockall(0b0001111111111000));
+
+    // On Linux, munlockall seems to have no perms or limits issues, so it should
+    // always be successful.  This at least lets us exercise the code in the
+    // posix wrapper on one platform to know it's not horribly broken.  This
+    // could have a real effect on the testing environment if it were already
+    // holding locked memory, but it shouldn't be.
+    if (native_os == .linux)
+        try posix.munlockall();
+}
diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index c6a4f9f78f5b..d9d6b94c20d1 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -49,6 +49,26 @@ pub fn expectError(expected_error: anyerror, actual_error_union: anytype) !void
     }
 }
 
+/// This function is intended to be used only in tests. It prints diagnostics to stderr
+/// and then returns a test failure error when actual_error_union is not one of the
+/// errors in expected_errors.
+pub fn expectErrors(expected_errors: []const anyerror, actual_error_union: anytype) !void
+{
+    if (actual_error_union) |actual_payload| {
+        print("expected one of {any}, found {any}\n", .{ expected_errors, actual_payload });
+        return error.TestUnexpectedError;
+    } else |actual_error| {
+        for (expected_errors) |e|
+            if (actual_error == e)
+                return;
+        print("expected one of {any}, found error.{s}\n", .{
+            expected_errors,
+            @errorName(actual_error),
+        });
+        return error.TestExpectedError;
+    }
+}
+
 /// This function is intended to be used only in tests. When the two values are not
 /// equal, prints diagnostics to stderr to show exactly how they are not equal,
 /// then returns a test failure error.