纤细通泉草（学名：Mazus gracilis）为玄参科通泉草属下的一个种。

Mazus gracilis is a plant species native to the Provinces of Henan, Hubei, Jiangsu, Jiangxi and Zhejiang in China. It grows on lake shores, river banks, and other moist areas at elevations below 800 m.

Mazus gracilis is a perennial herb spreading by means of stolons running along the surface of the ground for as far as 30 cm (12 inches). Leaves are up to 2.5 cm long. Flowers are born in axillary racemes. Flowers are yellow, white or purple, sometimes with spots of another color.