Kate, 35, and Derek, 29, sparked romance rumors when they were spotted together as recently as this past weekend at the Nice Guy Restaurant in Los Angeles, according to Us Weekly. One eyewitness says the two ate dinner, drank and stayed past closing.
Kate and Derek have been friends for three years, and he's even given the super-fit actress dance lessons in the past.
kate hudson matt bellamy
Is Kate Hudson dating Derek Hough after calling off engagement?
NEW YORK, NY - APRIL 17: (Exclusive Coverage) Kate Hudson and Matt Bellamy attend the Breast Cancer Foundation's Hot Pink Party at the Waldorf Astoria Hotel on April 17, 2013 in New York City. (Photo by Kevin Mazur/WireImage)
LONDON, ENGLAND - JULY 08: Matt Bellamy and Kate Hudson attend the Novak Djokovic Foundation inaugural London gala dinner at The Roundhouse on July 8, 2013 in London, England. The foundation supports vulnerable and disadvantaged children, especially in Djokovics native Serbia. (Photo by Tim P. Whitby/Getty Images for Novak Djokovic Foundation)
VENICE, ITALY - AUGUST 29: Actress Kate Hudson and Matt Bellamy attend 'The Reluctant Fundamentalist' Premiere And Opening Ceremony during the 69th Venice International Film Festival at Palazzo del Cinema on August 29, 2012 in Venice, Italy. (Photo by Pascal Le Segretain/Getty Images)
VENICE, ITALY - AUGUST 29: Actress Kate Hudson and Matt Bellamy attend 'The Reluctant Fundamentalist' Premiere And Opening Ceremony during the 69th Venice International Film Festival at Palazzo del Cinema on August 29, 2012 in Venice, Italy. (Photo by Gareth Cattermole/Getty Images)
US actress Kate Hudson (R) and British musician Matt Bellamy arrives for the opening ceremony of the 69th Venice film festival on August 29, 2012 at Venice Lido. 'The reluctant fundamentalist' by Indian film director Mira Nair will open the 69th Venice film festival, the cinema mostra. AFP PHOTO / GABRIEL BOUYS (Photo credit should read GABRIEL BOUYS/AFP/GettyImages)
LONDON, UNITED KINGDOM - AUGUST 22: Kate Hudson and Matt Bellamy seen heading to a gym in Hampstead on August 22, 2012 in London, England. (Photo by Neil Mockford/FilmMagic)
LONDON, UNITED KINGDOM - MARCH 09: Matt Bellamy and Kate Hudson are seen on March 09, 2012 in London, United Kingdom. (Photo by TOE/Bauer-Griffin/GC Images)
LONDON, ENGLAND - MARCH 07: (EMBARGOED FOR PUBLICATION IN UK TABLOID NEWSPAPERS UNTIL 48 HOURS AFTER CREATE DATE AND TIME. MANDATORY CREDIT PHOTO BY DAVE M. BENETT/GETTY IMAGES REQUIRED) Kate Hudson (L) and Matt Bellamy attend the Hawn Foundation UK launch event hosted by Goldie Hawn at Annabels on March 7, 2012 in London, England. (Photo by Dave M. Benett/Getty Images)
NEW YORK - NOVEMBER 10: (ITALY OUT, NY DAILY NEWS OUT, NY NEWSDAY OUT) Kate Hudson and boyfriend Matt Bellamy walk in the city on November 10, 2010 in New York City. (Photo by Arnaldo Magnani/Getty Images)
BEVERLY HILLS, CA - OCTOBER 18: Honoree Kate Hudson and musician Matt Bellamy attend ELLE's 17th Annual Women in Hollywood Tribute at The Four Seasons Hotel on October 18, 2010 in Beverly Hills, California. (Photo by Jason Merritt/Getty Images For Elle Magazine)
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"My heart is really in contemporary jazz, but lately I've been ballroom dancing with Derek Hough," she told Shape magazine in 2013. "It's been a real blast."
Just last month, the two attended Goldie Hawn's "Love In For Kids" benefit, where they were snapped having a friendly conversation. They two also posed for pictures together, Kate showing off her toned arms in a sleeveless white dress and Derek looking dapper in a dark suit.
This of course isn't the first in-demand Hollywood starlet Derek has been linked to. Derek has also been rumored to have romanced Lauren Conrad, Nina Dobrev and Nikki Reed in the past.
News broke of Kate and Matt's split on Monday, when his rep confirmed that the two have been separated "for some time now," after four years together. The two got engaged in April 2011, three months before Kate gave birth to their son, three-year-old Bingham Hawn Bellamy.
"They remain very close friends and committed co-parents," Bellamy's rep told ET.
In May, ET's Rocsi Diaz caught up with the How to Lose a Guy in 10 Days actress at the launch of her workout company Fabletics' Spring 2014 collection, who at the time said she was still planning on marrying Bellamy despite their long engagement.
"Matt and I -- not yet," she said when asked about the possibility of an upcoming wedding between the two. "I think we will for the kids at some point, but it's still just not something we're focused on planning."