This is not a good look for this country singer.

Sam Hunt's wife has filed to end their 5-year marriage, citing infidelity as the reason.
Hannah Lee Fowler claims in her legal docs, obtained by TMZ that Sam is "guilty of inappropriate marital conduct," and she goes on ... "guilty of adultery."

Elsewhere in the docs, Fowler claims that “all hopes of reconciliation are exhausted.” Hunt has yet to comment.

Sam and Hannah had not announced she was pregnant, but in the docs, she says she's due in May.

The docs were filed in Tennessee, which isn't a no-fault divorce state. She's asking for alimony. She also wants primary custody of their soon-to-be-born child. And, she wants child support as well.

It's unclear if they have a prenup. As for alimony, Hannah wants, "transitional alimony, rehabilitative alimony, and alimony in future."