长臂天牛（学名：Acrocinus longimanus）为天牛科粗天牛亚科的动物。分布于拉丁美洲地区（北起墨西哥，南至阿根廷北部）的热带雨林。雄虫前肢特长，属于大型天牛，体长可达约 7.6 公分。

与少数种类的拟蝎具有偏利共生的关系（已知有三种，分别是 Cordylochernes scorpioides, Lustrochernes intermedius 与 Parachelifer lativittatus），拟蝎会短时间的附着在长臂天牛身上，借由长臂天牛移动而达到移动至他处的目的。

在英文中被称为「Harlequin beetle」，亦即「滑稽的甲虫」，形容甲壳上的花纹，像小丑身上的衣服；种名「longimanus」在拉丁文是指「长的手」；形容雄虫细长的前肢。

The harlequin beetle (Acrocinus longimanus) is a large tropical longhorned beetle native to the Americas, especially from southern Mexico to Brazil in South America. The harlequin beetle feeds on sap and is given this name because of its elaborate pattern of black, red and greenish yellow markings on the wing covers of both sexes. The species name longimanus is a Latin word that refers to the extremely long forelegs (manus) of the males, which are usually longer than the beetle’s entire body. As an adult, the species is very large, with a body that can measure nearly 76 mm (3 inches) in length. It is also famous for carrying pseudoscorpions as a form of phoresy.