The Frost Report was the television show that brought several future Monty Python members together before Monty Python's Flying Circus. The BBC satirical sketch series was hosted by David Frost and ran from 1966 to 1967.
John Cleese, Graham Chapman, Eric Idle, Terry Jones, and Michael Palin all worked on The Frost Report in different writing and performing capacities. Their collaboration helped them develop the fast, literate, absurd style that would later become central to Monty Python. Cleese and Chapman formed one important writing partnership, while Jones and Palin developed another.
The programme was not itself a Monty Python series, and Terry Gilliam was not part of this particular pre-Python group. Gilliam joined the Python project as its American-born animator, bringing a visual language shaped partly by his earlier work on Do Not Adjust Your Set.
Other pre-Python programmes can cause confusion. At Last the 1948 Show featured several related performers, while Do Not Adjust Your Set featured Jones, Palin, and Idle alongside Gilliam's animations. The Frost Report is the canonical answer because it is credited with first bringing the five British Pythons together.