Posting via The Rolling Stones' Facebook account, Jagger has shared his thoughts on L'Wren's shock death, describing her as having "a great presence" and "much admired" talent.
Mick and L'Wren attended a Harper's Bazaar party in November 2013
"I am still struggling to understand how my lover and best friend could end her life in this tragic way," reads the statement.
"We spent many wonderful years together and had made a great life for ourselves.
"She had great presence and her talent was much admired, not least by me.
"I have been touched by the tributes that people have paid to her, and also the personal messages of support that I have received.
"I will never forget her, Mick."
Jagger recently arrived in Perth to begin a 14-date tour with The Rolling Stones, however, upon learning of L'Wren's sudden death the band have cancelled the first night of their tour.
It is not yet known whether the remaining concerts will go ahead as planned.
The pair are thought to have been dating since 2001 and a rep for Jagger confirmed that the pair were still in a relationship at the time of her death.
Tributes to L’Wren have poured in online, with many celebs taking to Twitter to share their sadness at the unexpected and shocking news, including Mick's ex-wife Bianca who tweeted: "Heartbroken to learn of the loss of the lovely and talented L'Wren Scott. My thoughts and prayers are with her family. May she rest in peace."