A Fist Within Four Walls (Chinese: 城寨英雄; Cantonese Yale: Sìngjaaih Yīnghùng) is a 2016 Hong Kong martial arts action television drama produced by Jazz Boon and TVB. It premiered on TVB Jade in Hong Kong, Astro On Demand in Malaysia and TVB First in Singapore on 1 August 2016. The final episode aired on 28 August 2016, totalling 28 episodes.

A Fist Within Four Walls takes place in the triad-ridden Kowloon Walled City in the early 1960s. The plot revolves around Chor Au-kuen, a gifted martial arts novice who takes on the duty of protecting the walled city against evildoers. A Fist Within Four Walls is the highest-rated drama of 2016, and its final episode was the second most-watched series finale of the year in Hong Kong. It received generally positive reviews during its broadcast.

The drama received multiple awards and nominations at the StarHub TVB Awards and the TVB Star Awards in Malaysia, winning Favourite Drama, Favourite Actor (Ruco Chan), and Favourite Actress (Nancy Wu) at both ceremonies. It won six awards at the TVB Anniversary Awards, including Best Drama, Best Actor (Chan), Best Actress (Wu), Most Popular Male Character (Benjamin Yuen), Most Popular Female Character (Grace Wong), and Most Popular Drama Theme Song ("Never Know You Are the Best").