NSL Buses (previously known as NCP Challenger) was an operator of London Buses. It was founded by Matt Larkin on 12 November 2005.
NSL was based in Middlesex, and was owned by NSL Services Group, which emerged from the car park operator National Car Parks as NCP Services in 2007.
On 13 November 2009, NSL Buses was bought by the former Transdev London, which today is transferred to London United Busways.