The couple, who have a baby son, Lennon, married three years ago.
The 32-year-old actress has recently been seen without her wedding ring and was spotted on Friday loading up items from the home they shared in north London.
Asked if she was disappointed at the split, Kensit said: "It's over - no, I'm actually relieved.
"It's been over for quite a long time really," she said on ITV's London Tonight programme.
Kensit denied she had been through a rough time and said she still regarded Liam as a friend, and wished him well.
The couple confirmed two weeks ago they had put their Primrose Hill house up for sale, fuelling speculation that they were to split.
It is not the first time that the pair have separated during their volatile relationship.
Kensit left home for a while last year and was said to be in tears most days while filming her movie Janice Beard: 45 WPM because of the upset.
In 1998, Liam denied reports that the marriage was in trouble after he allegedly threw his wife out of their home following a drinking session.
The row was the culmination of a series of disputes about the singer's alleged womanising and wild man antics - but within weeks they were back together again.
The relationship was thought to be on a more even keel after the birth of Lennon last September but the strains became apparent again in recent weeks.
Third marriage
Gallagher has been touring with Oasis in Europe during the last few weeks and has been out of the UK for most of the year because of the band's commitments.
He has a similarly fragile relationship with his brother Noel. A row between the pair prompted Noel to quit touring with the band for their European dates.
It is the third marriage of Kensit's to break down. She was previously married to musician Dan Donovan of Big Audio Dynamite, then Jim Kerr from Simple Minds, with whom she had a son James.
That marriage ended in 1996 and the actress wed Gallagher in April 1997.