In her new role, Tennant will assume editorial leadership for UKTV's portfolio of 10 channels and all related multiplatform activities. She previously oversaw ITV's digital channels ITV2, ITV3 and ITV4.
UKTV - jointly owned by BBC Worldwide and Virgin Media - has been searching for a permanent controller ever since previous incumbent Matthew Littleford joined BBC Worldwide for the launch of the international version of BBC iPlayer.
Tennant has a strong track record in acquisitions and commissioning, including responsibility for commissioning Martina Cole's Ladykillers, Matthew Kelly's Forensic Casebook and drama series Ladies of Letters.
UKTV chief executive Darren Childs said: "Emma will be instrumental in leading UKTV through the evolution of its next creative challenge and I am delighted she will be joining the team. Her strong commercial success combined with enviable creative, editorial and leadership qualities make Emma the perfect appointment.
"UKTV is embarking on another renaissance following our phenomenally successful rebrand. We're Sky's largest HD provider; we are launching an exciting VOD service with Sky+ Anytime and Dynamo: Magician Impossible has been watched by 7.3 million individuals since premiere. Emma is the right commercial and creative leader to maximise the myriad of opportunities we have."
Tennant said of her move: "I have had a wonderful time at ITV and am incredibly proud of the success the digital channels teams have had.
"However, I am very excited by this new challenge and to be joining UKTV at this pivotal time. The network continues to go from strength to strength as it maximises its enviable mix of BBC content, breakout commissions and third-party acquisitions."
Tennant started her career at Living TV, where she helped set up the channel's strategy and acquired hit shows such as CSI, Next Top Model and Will & Grace. She moved to ITV3 in October 2005, assuming the role of controller of ITV3 and CITV in 2007, before becoming controller of all ITV digital channels in 2009.
Tennant will sit on UKTV's executive leadership team and report to Childs and the new director of BBC Vision, George Entwhistle. Her start date will be announced shortly.