Vanessa Bryant filed legal docs Friday afternoon, citing "irreconcilable differences."
Sources connected with the couple tell TMZ ... Vanessa -- who stuck by Kobe after he was charged with sexually assaulting a Colorado woman in 2003 -- decided to end the marriage because she believes Kobe has been unfaithful ... again.
As one source puts it, "She's been dealing with these incidents for a long time and has been a faithful wife, but she's finally had enough," adding, "This one is the straw that broke the camel's back."
And our sources say ... Kobe "desperately" wants to win Vanessa back and will do "whatever it takes" to save their 10 1/2 year marriage.
According to the legal docs, Vanessa is asking for of their 2 daughters -- 8-year-old Natalia and 5-year-old Gianna -- but Vanessa is asking that Kobe get visitation rights, which means she wants the kids in her care most of the time.
We've learned the couple has NO PRENUP, so 29-year-old Vanessa is entitled to half of the empire Kobe built over the last decade.