ITV1 (formerly known as ITV) is a British free-to-air public broadcast television channel owned and operated by the British media company ITV plc. It provides the Channel 3 public broadcast service across all of the United Kingdom except for the central and northern areas of Scotland where STV provides the service.

ITV1 as a consistent national channel (with dedicated slots for regional news and other regional programmes) evolved out of the old ITV network – a federation of separately owned regional companies which had significantly different local schedules and branding. During the 1990s, the differences between the schedules in each region gradually reduced – partly through the consolidation of ownership and partly through the standardisation in the volume and scheduling of regional programmes.

In 2002, a major change of appearance occurred when all ITV regions in England and Wales adopted national continuity. Regional logos vanished and regional names were mentioned only before regional programmes. Effectively this left ITV1 in England and Wales looking like a national channel with slots for regional opt-outs – like BBC One – rather than a group of independent regional broadcasters sharing programmes.

The unification was consolidated in 2004 when Granada plc acquired Carlton Communications to form ITV plc. By then, the two companies had acquired all the regional Channel 3 companies in England and Wales. ITV plc later acquired Channel Television in the Channel Islands and UTV in Northern Ireland.

ITV1 is today the biggest and most popular commercial television channel in the United Kingdom. ITV1, and its predecessor regional channels, have contended with BBC One for the status of the UK's most watched television channel since the 1950s. However, in line with other terrestrial channels, ITV1's audience share has fallen as a result of availability of multi-channel television in the UK.