First Cymru is an operator of bus services in South West Wales. It is a subsidiary of FirstGroup. With its headquarters previously in Swansea, it is now part of the First Wales and West region which also covers Bristol, Bath and Worcester, with its headquarters in Bristol. With 220 vehicles, it is the second largest bus operator in Wales after Stagecoach South Wales.

In 1987, South Wales Transport was sold during the privatisation of the National Bus Company in a management buy out.

In February 1990, along with Brewers Motor Services and United Welsh Coaches, South Wales Transport was sold to Badgerline. All initially retained their trading names but following Badgerline merging with GRT Group in April 1995 to form FirstBus, all Welsh operations were rebranded as First Cymru.

The company operates 104 bus services in the South West Wales area, in and between Haverfordwest, Pembroke, Tenby, Carmarthen, Ammanford, Llanelli, Swansea, Pontardawe, Neath, Port Talbot, Maesteg, Bridgend and Cardiff. Following contract wins in April 2024, their network was expanded in Pembrokeshire and the Vale of Glamorgan, incorporating locations such as Narberth, Whitland, Barry and Cardiff Airport.

In addition to internal South Wales work, First Cymru also operate the TrawsCymru T1 service between Carmarthen and Aberystwyth under contract to the Welsh Government using Yutong E12 electric vehicles leased from them.

First Cymru branding was previously used across the network. However, local 'Swansea and the Bay', 'Western Welsh', 'Neath & Port Talbot' and 'Bridgend and County' branding began to be applied to services in its sub-areas. All future repaints will now however be in the national blue and silver First Bus livery.

First Cymru has provided dedicated services for students of Swansea University for a number of years. The original service, known as 'Bright Orange Bus', linked Hendrefoilan Student Village to Singleton Campus and the City Centre. The service was expanded to the Bay Campus when it opened in 2015 and renamed 'Campus to Campus'. A new route was also introduced between the two campuses via Sketty, Uplands and Swansea railway station. The network was redesigned and rebranded 'Unibws' following the closure of Hendrefoilan Student Village in the summer of 2023. Newly numbered services 89-92 link the two campuses with the city centre, Sketty, Uplands and new student accommodation in the Parc Tawe, railway station and Morfa Road areas. Night buses N91 and N92 operate until around 4am in the term time.

First Cymru operates park & ride sites, which are located at Fabian Way and Landore in Swansea.