diff --git a/libc/include/locale.h b/libc/include/locale.h
new file mode 100644
index 0000000000..74c82cb7fd
--- /dev/null
+++ b/libc/include/locale.h
@@ -0,0 +1,63 @@
+#pragma once
+
+#include <stddef.h>
+#include <sys/cdefs.h>
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/locale.h.html#tag_13_24
+
+#define LC_ALL		1
+#define LC_COLLATE	2
+#define LC_CTYPE	3
+#define LC_MESSAGES	4
+#define LC_MONETARY	5
+#define LC_NUMERIC	6
+#define LC_TIME		7
+
+#define LC_COLLATE_MASK		0x01
+#define LC_CTYPE_MASK		0x02
+#define LC_MESSAGES_MASK	0x04
+#define LC_MONETARY_MASK	0x08
+#define LC_NUMERIC_MASK		0x10
+#define LC_TIME_MASK		0x20
+#define LC_ALL_MASK			0x3F
+
+__BEGIN_DECLS
+
+struct lconv
+{
+	char*	currency_symbol;
+	char*	decimal_point;
+	char	frac_digits;
+	char*	grouping;
+	char*	int_curr_symbol;
+	char	int_frac_digits;
+	char	int_n_cs_precedes;
+	char	int_n_sep_by_space;
+	char	int_n_sign_posn;
+	char	int_p_cs_precedes;
+	char	int_p_sep_by_space;
+	char	int_p_sign_posn;
+	char*	mon_decimal_point;
+	char*	mon_grouping;
+	char*	mon_thousands_sep;
+	char*	negative_sign;
+	char	n_cs_precedes;
+	char	n_sep_by_space;
+	char	n_sign_posn;
+	char*	positive_sign;
+	char	p_cs_precedes;
+	char	p_sep_by_space;
+	char	p_sign_posn;
+	char*	thousands_sep;
+};
+
+typedef int locale_t;
+
+locale_t		duplocale(locale_t);
+void			freelocale(locale_t);
+struct lconv	localeconv(void);
+locale_t		newlocale(int, const char*, locale_t);
+char*			setlocale(int, const char*);
+locale_t		uselocale(locale_t);
+
+__END_DECLS