狼牙修（马来语：Langkasuka）是古代东南亚的印度化国家之一，其领土包括今马来半岛东岸北大年以东和东北地区，约位于东经101°18'，北纬6°48'，及今马来西亚的吉打州。

狼牙修在宋代称为“凌牙斯加”、元代称为“龙牙犀角”、明代称为“狼西加”。“Langkasuka”一词首见于，印度尼西亚11世纪泰米尔文碑铭作 Ilangasongam,14世纪《爪哇史颂》（Nagarakrtagama），作Langkasuka，16世纪出版的阿拉伯文《吉打纪年》（Kitab al-Minhaj al-fakhir fi-ilm al-bahr al-zakhir）作Langashuka。“Langkasuka” 的得名或来自印度文化，依照印度的佛经《枵伽经》里的记载，Lanka是传说中一个在马来亚峰(英文：Mount Malaya)上面的山城；而在梵文中Sukha乃是“快乐世界─Sukhavati”一词中的前半截。因此Langkasuka或取义于“快乐的马来半岛山城”。

Langkasuka (langkha Sanskrit for "resplendent land" -sukkha for "bliss") was an ancient Hindu-Buddhist Malay kingdom located in the Malay Peninsula. Another possible source of its name could be the combination of (-langkha Sanskrit for "resplendent land" – and Ashoka in tribute to the legendary Mauryan Hindu warrior king who eventually became a pacifist after embracing the ideals espoused in Buddhism), the ancient kingdoms of the Malay Isthmus – Langkasuka having been one of them – believed by some scholars to have been first founded or rebuilt by emissaries or descendants of Ashoka from Magadha in India.