通俗拉丁语（拉丁文：sermo vulgaris，意为“通俗话”，又叫民间拉丁语，或流行拉丁语），是古典拉丁语在法国、意大利、西班牙、葡萄牙、罗马尼亚等地的民间通俗变体。中世纪早期开始分化，至九世纪成为罗曼语支的一支。

通俗拉丁语的语法比古典拉丁语简单得多，在语言学上体现了古典拉丁语作为一种综合语到今日的法语、意大利语、西班牙语、葡萄牙语、罗马尼亚语等语言作为一种分析语的过渡。

今日罗曼语族诸语言都是直接从通俗拉丁语演变而来。

Vulgar Latin or Sermo Vulgaris ("common speech") is a generic term for the nonstandard (as opposed to classical) sociolects of Latin from which the Romance languages developed. Works written in Latin during classical times used Classical Latin rather than Vulgar Latin, with very few exceptions (most notably sections of Gaius Petronius' Satyricon). Because of its nonstandard nature, Vulgar Latin had no official orthography. Vulgar Latin is sometimes also called colloquial Latin, or Common Romance (particularly in the late stage). In Renaissance Latin, Vulgar Latin was called vulgare Latinum or Latinum vulgare.