臂形草属（学名：Brachiaria）是禾本科下的一个属，为一年生或多年生草本植物。该属共有50种，分布热带地区。

Brachiaria, or signalgrass, is a genus of plants in the grass family native to tropical and subtropical regions of Asia, Africa, Australia, southern Europe, the Americas, and various islands. There are over 100 species.

Some species are cultivated as forage. Some species of Brachiaria were probably first introduced unintentionally to the Americas in the colonial period, from slave ships. B. decumbens was introduced to Brazil in 1952 and B. ruziziensis in the 1960s. Brachiaria is the most widely used tropical grass in Central and South America, with about 40 million hectares planted in Brazil alone.