Kamen Rider Black RX (仮面ライダーBLACK RX, Kamen Raidā Burakku Āru Ekkusu) is a Japanese tokusatsu superhero television series produced as part of the Kamen Rider series. The ninth show in the franchise, it was produced by Toei Company, and aired on the MBS, TBS and other JNN affiliates from October 23, 1988, to September 24, 1989. The series is a direct sequel to Kamen Rider Black and the first to feature a team-up with the past Riders since the 1984 TV special Birth of the 10th! Kamen Riders All Together!!. For distribution purposes, Toei refers to this television series as Black Kamen Rider RX.

This was also the last installment of the Kamen Rider series to be produced in the Shōwa era and the first to be produced in the Heisei one — Episode 11 was delayed by one week following Emperor Hirohito's death.

The series was adapted by Saban in North America as Masked Rider. The show featured a heavily altered story and all-new characters, in an attempt to fit the series in as a spin-off of Power Rangers.