Long Arm of the Law (省港旗兵, lit. "Red Guards in Guangzhou and Hong Kong") is a 1984 Hong Kong crime film directed by Johnny Mak Tong-hung.

Five men try to enter Hong Kong surreptitiously, meeting their leader there, to rob a jewellery store. One is shot and killed by Chinese border guards. Police investigating another robbery attempt at the same store spot their car acting suspiciously while they are casing it and give chase, with the robbers only escaping by opening fire and stealing a taxi.

Before the robbery has taken place, they are employed by a local triad to kill someone. The target turns out to be a policeman and they have to carry out the robbery while hiding from the police searching for them.

There were three sequels: Long Arm of the Law II (1987), Long Arm of the Law III (1989) and Long Arm of the Law IV: Underground Express (1990).