National Welsh Omnibus Services was a bus company which operated in south-east Wales and in the Forest of Dean area of Gloucestershire from 1978 to 1992. It used the trading name National Welsh and its Welsh equivalent Cymru Cenedlaethol.
National Welsh had its origins in the Western Welsh Omnibus Company, formed in 1929 as a subsidiary of British Electric Traction. The Great Western Railway transferred its bus services in South and West Wales to the company and took a financial interest, hence the name. The railway interest passed to the British Transport Commission in 1948, but Western Welsh was not fully nationalised until 1967 when BET sold its bus interests to the Transport Holding Company. The company passed to the National Bus Company in 1969.
In 1970 and 1971, the NBC transferred Western Welsh's operations west of Bridgend to its subsidiaries South Wales Transport and Crosville. In return Western Welsh took over the operations of Rhondda Transport.
In 1978, the National Bus Company transferred the operations of its subsidiary Red & White Services to Western Welsh and renamed the merged company National Welsh/Cymru Cenedlaethol (the latter an incorrect translation, which should be Cymraeg Cenedlaethol). The company's area of operations thus became South-East Wales and the Forest of Dean area of Gloucestershire.
In 1987, National Welsh was sold to its management, which struggled to make a profit. In January 1991, the Eastern Division of National Welsh, which included depots in Cwmbran, Crosskeys, Brynmawr and Chepstow, was sold to Western Travel Group. Western Travel renamed this division (with its outstations at Abergavenny, Brecon, Cinderford, Ross and Lydney), Red & White Services Ltd. The Company traded as Red & White and introduced a livery similar to National Welsh, but with a grey band instead of green.