A new guidance law, called biased retro proportional navigation (BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results (trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation (BPN), proportional navigation and retro-proportional navigation. The results show that, at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.