Ewan cites irreconcilable differences as the reason he wants to end his marriage to Eve Mavrakis.

McGregor, repped by attorney Fahi Takesh Hallin, wants joint custody of the couple's 3 minor children. Eve, whose lawyer -- disso queen Laura Wasser -- filed her answer at the same time, is asking for sole physical custody with visitation going to Ewan.

McGregor says in the docs he's willing to pay spousal support. As for property ... our sources say there is no prenup so the assets should be evenly divided.

The date of separation is listed as May 28th of last year.

News of Ewan and Eve's split hit in October ... with reports saying the two had separated as early as May. The announcement came shortly after pics surfaced of Ewan kissing his "Fargo" co-star, Mary Elizabeth Winstead, at a London cafe.