The BAC One-Eleven (or BAC-111/BAC 1-11) was an early jet airliner produced by the British Aircraft Corporation (BAC).

Originally conceived by Hunting Aircraft as a 30-seat jet, before its merger into BAC in 1960, it was launched as an 80-seat airliner with a British United Airways order on 9 May 1961.

The prototype conducted its maiden flight on 20 August 1963, and it was first delivered to its launch customer on 22 January 1965.

The 119-seat, stretched 500 series was introduced in 1967.

Total production amount to 244, until 1982 in the United Kingdom and between 1982 and 1989 in Romania where nine Rombac One-Eleven were licence-built by Romaero.

The short haul, narrowbody aircraft was powered by aft-mounted Rolls-Royce Spey low-bypass turbofans, a configuration similar to the earlier Sud Aviation Caravelle and later Douglas DC-9.

It also competed with early Boeing 737 variants and was used by several US carriers, as well as multiple British, overseas and European airlines, including Romanian operators.

It was replaced by the newer Airbus A320 and later 737 variants, as well as by the Bombardier CRJ200 regional jet.

Noise restrictions accelerated its transition to African carriers in the 1990s, and the last BAC One-Eleven was retired in 2019.