Kate Louise Thornton (born 7 February 1973) is an English journalist and broadcaster, best known as the first presenter of The X Factor (2004–2006) and for presenting daytime shows including Loose Women (2009–2011) and This Morning (2009–2012). In 2010, she co-presented the first series of 71 Degrees North alongside Gethin Jones.

In 1995, at 21 she became the youngest editor of pop magazine Smash Hits. She left a year later, having been unable to prevent a further slide in sales of the magazine. In 1997, she became a Features Editor at the Sunday Times, a post she held until 2001, and also a contributing Editor for magazine Marie Claire, in which position she continued until 2003.

Whilst undertaking these new editorial roles, Thornton began a second career in television. In February 1997, Thornton was given her first TV presenting job, on the ITV current affairs programme Straight Up. She was tasked with putting together a photo tribute with music for Princess Diana on the day of her death. In an interview in March 2011, Thornton said: "...because it was a Sunday, the music library was shut and the only thing I had in my car, the only piece of music that was appropriate was "Candle in the Wind" from Elton John's greatest hits." Colleagues attributed the subsequent airplay and then the re-recording of the song to this event. Thornton is quoted as having been doubtful initially, but later having come to accept the possibility: "I never dared to assume for one minute that I was the link. But Nick Knowles (co-presenter on the show) has convinced me that whatever came as a result of it was all down to me."

Thornton was the first presenter of the UK series of The X Factor. She presented three series of the show from 2004 until 2006 before being replaced by Dermot O'Leary. Thornton later anchored ITV's daytime series Loose Women, in rotation with Andrea McLean. She presented 233 episodes of the show from 2009. She, and fellow Loose Woman Zoë Tyler, were replaced in 2011 by Carol Vorderman and Sally Lindsay.

Thornton was a regular stand-in presenter on This Morning and in 2010, she co-presented the first series of 71 Degrees North alongside Gethin Jones. Neither returned for the second series. In 2010, she narrated The Nation's Favourite Abba Song. Thornton also presented A Night with Will Young in 2011. She guest presented six episodes of Lorraine in 2012.

Thornton also presented Gravity Games for BBC Two, Women: The Naked Truth Honest for Channel 4 and Breasts Uncupped for Sky1.

She currently hosts The Royal Beat - a topical royal chat show - on True Royalty TV, which is available via Amazon Prime and Apple TV. According to the blurb on the official website: “Every episode goes behind the headlines to bring to viewers fresh, detailed insight into the biggest royal stories from the UK and around the world.”

Thornton has presented a number of programmes for BBC Radio 2 since 2002. Along with presenting, Thornton was also the writer of the radio documentary From Band to Brand in 2004, and the creator of the radio series Line of Enquiry, inviting an audience to put questions to a number of celebrities, which began in 2007.