William Nicholas Stone Courtney was an Egyptian-born British actor. He was best known for his long-running role as Brigadier Lethbridge-Stewart in the BBC science fiction television series Doctor Who.

Alistair Gordon Lethbridge-Stewart, fully Brigadier Sir Alistair Gordon Lethbridge-Stewart, generally referred to simply as the Brigadier, is a fictional character in the British science fiction television series Doctor Who, created by writers Mervyn Haisman and Henry Lincoln and played by Nicholas Courtney. He is one of the founders of UNIT, an international organisation that defends Earth from alien threats, and serves as commander of the British contingent. Presented at first as reluctant to accept the continuing aid of the Doctor, over time the Brigadier became one of the Doctor's greatest friends and his principal ally in defending Earth.