Western Welsh was a Welsh bus operating company, based in Cardiff covering South Wales and the northern parts of the West Country. Formed in 1920, it was nationalised when the BET Group sold their bus interests to the Transport Holding Company in 1967. From 1969 W.W. became a part of the National Bus Company and several years later was a component of the newly formed, but ill-fated, National Welsh operation.

Established in 1920 in Cardiff by a brewing family, South Wales Commercial Motors grew by acquisition,^[1] eventually operating bus services in South Wales as far west as St David's and Tenby in Pembrokeshire, and as far north as Brecon via the South Wales Valleys. In 1927, the company came to an agreement with the Great Western Railway to take over their bus services in both South Wales, and areas of southern Gloucestershire and northern Somerset surrounding Bristol and Bath. In return, the GWR took a minority share holding in the renamed Western Welsh.^[2]

In 1931, the GWR sold their bus company shareholdings to British Electric Traction, who continued expansion of the company by acquisition. As with other BET companies, Western Welsh's fleet included a significant number of AEC and Leyland types, including AEC Bridgemasters and Albion Nimbuses, all of which appeared in the company's familiar all-red livery.

Although entire UK railway network was nationalised in 1948 when they passed to the British Transport Commission, many bus services remained in private hands.

After BET sold its operations to the government, Western Welsh became part of the National Bus Company. In 1970, NBC transferred Western Welsh's operations west of Bridgend to its subsidiaries South Wales Transport and Crosville Motor Services. The company continued to operate further east until 1978, when it was merged with Red & White Services to form National Welsh Omnibus Services. National Welsh was privatised in 1987, and collapsed in 1992.