ITV3 is an entertainment television channel in the United Kingdom that is owned by ITV Digital Channels Ltd, a division of ITV plc. The channel was launched on 1 November 2004. ITV3 is the sixth largest UK television channel by audience share and the largest after the five analogue terrestrial services - a position previously held by its sister station ITV2.

ITV3 was launched on the terrestrial (Freeview), cable (Virgin Media) and digital satellite (Sky) on 1 November 2004 at 21:00. It is also available on TalkTalk TV IPTV.

The channel had been available from launch on UPC Ireland, but was pulled on 22 March 2006. This is believed to have been at the request of ITV plc, which had previously barred Irish newspapers from publishing details of ITV channels and regions other than UTV and Men & Motors. The channel had already been (and remains) available to Irish viewers on free-to-air satellite for some time, however it has not been listed in the Sky electronic programme guide since its removal on 25 January 2006. ITV3 returned to UPC Ireland in the Republic of Ireland on 4 January 2010. On 1 April 2011, ITV3 was removed from UPC Ireland along with ITV2 and ITV4 due to the expiry of a carriage agreement between UPC and ITV. UPC Ireland claim that ITV is not in a position to renegotiate the deal because ITV had struck a deal with another channel provider to provide it with exclusive rights to air certain content from the channels. Conversely, UPC Ireland also claims to have been in discussions right up to the last moment in order to continue broadcasting the channels. ITV2, ITV3 and ITV4 were restored to the UPC Ireland line-up on 20 December 2011. TV3 Ireland and its sister channel 3e already hold carriage agreement to air certain ITV content within the Republic of Ireland, alternatively UTV is available within the Republic. ITV2 is available along with ITV3 and ITV4 within Switzerland, all three channels are available on SwisscomTV and UPC Cablecom.