'Melrose Place' Star Courtney Thorne-Smith Files for Divorce

Courtney Thorne-Smith has filed for divorce from her husband, Roger Fishman, nearly four years after she says they separated ... TMZ has learned.

The veteran actress filed the docs without a lawyer earlier this week ... citing the boilerplate irreconcilable differences.

Thorne-Smith lists the date of separation as September 1, 2021 ... so, it looks like the two have been living separate lives for some time now.

The two married on New Year's Day 2007 ... and, they welcomed their only child -- Jacob Emerson Fishman -- about a year later.

He's turns 18 next year, so they won't be co-parenting a minor for much longer. Thorne-Smith is asking the court for joint legal and physical custody of Jacob.

Courtney checked the box asking to terminate the court’s ability to award spousal support to either herself or her estranged husband.

This is Thorne-Smith's second marriage ... she married geneticist Andrew Conrad in 2000 but got divorced from him in 2001. She also dated her "Melrose Place" costar Andrew Shue back in the '90s.

Courtney's best known for playing Alison Parker on the hit primetime soap opera in 165 episodes of the show from 1992 to 1997. She's since starred on sitcoms like "Ally McBeal," "According to Jim," and "Two and a Half Men."