隆背张口蟹（学名：Chasmagnathus convexus），亦作隆脊张口蟹，是一种在东亚的特有种，常见于干潟，属于方蟹总科的弓蟹科，分布于北至日韩、南至越南北部。在日本及**，本物种又称作「滨蟹」。

本物种有两个不同的形式，主要是颜色的分别：有橄榄绿及紫色两种。这个分别相信是因为食性的分别而造成。与其他物种相比，本物种的尺寸算是比较大。其头胸甲有4.5至5厘米（1.8至2.0英寸）阔，横长近圆形。本物种主要是夜行性。

Chasmagnathus convexus is a common mud-flat crab of the family Varunidae, which is endemic to East Asia. In Japan, this crab is commonly called hamagani. This crab has two forms that differ in color; one is olive green and the other is purple. Differences in diet are believed to be responsible for the color variation between the two forms. C. convexus is large, relative to related crabs, and can reach 4.5 to 5 centimetres (1.8 to 2.0 in) wide across its carapace. It is predominantly nocturnal.