Lucas Giolito will enter the second half of the MLB season as a single man ... TMZ Sports has learned the White Sox star's wife just filed for divorce.
Ariana Dubelko filed the docs in a Los Angeles court on Monday afternoon. She cited "irreconcilable differences" as the reason for the split.
In her filing, Dubelko also asked for spousal support from the 28-year-old pitcher, who's making $10.4 million with Chicago this season.
Despite Dubelko filing, a rep for Giolito told us the split was "a mutually agreed upon and amicable decision made by both parties."
Lucas' rep added ... "Unfortunately the State of California does not allow for a joint filing."
Nonetheless, the breakup is a shocking one -- considering the two had dated since they were teenagers ... and were often seen showing big love to each other on their social media pages.
In fact, back in September 2022 ... Giolito filmed an ad for a Sox sponsor, and in it, he praised his marriage to Dubelko as one his "favorite" "unbeatable moments."
The two -- who did not have kids together -- got married in 2018 in a lavish wedding that featured a guest list which included MLB stars Jack Flaherty, Max Fried and James Shields.