Wessex Trains was a train operating company in the United Kingdom owned by National Express that operated the Wessex Trains franchise from October 2001 until March 2006, when the franchise was merged with the Great Western and Thames Trains franchises to form the Greater Western franchise.

In October 1996, Wales & West commenced operating the South West & Wales franchise in Wales and the West Country. It also operated services to Liverpool Lime Street, Manchester Piccadilly, Birmingham International, Southampton Central, Brighton and London Waterloo.

In 2001 the Strategic Rail Authority decided to re-organise the Valley Lines and Wales & West franchises, both being operated by National Express. Wales & West became Wessex Trains from October 2001.

Wessex Trains retained the West Country services with the Welsh services transferred to Wales & Borders although Wessex Trains operated services to Cardiff.

Wessex Trains ran the majority of local trains in the South West as seen in their route map, including retaining the Alphaline branding.

Services ran from Great Malvern and Cardiff to Brighton, Portsmouth, Weymouth and Penzance and on these secondary lines:

Wessex Trains inherited a fleet of Class 143s, Class 150s, Class 153s and Class 158s from Wales & West.

Wessex Trains leased Class 31 locomotives from Fragonset to haul a set of Mark 2 carriages from 2002 on services from Cardiff and Bristol Temple Meads to Brighton and Weymouth.