Wan Yai (Thai: หว้านใหญ่, pronounced [wâːn jàj]; Northeastern Thai: หว้านใหญ่, pronounced [wàːn ɲāj]) is a district (amphoe) of Mukdahan province, northeastern Thailand.

To the east across the Mekong River is the Laotian province of Savannakhet.

The minor district (king amphoe) Wan Yai was created on 16 September 1977, when the tambon Wan Yai, Pong Kham, and Bang Sai Noi were split off from Mukdahan district.

[2] The district is divided into five sub-districts (tambon), which are further subdivided into 44 villages (muban).

There are no municipal (thesaban) areas, and four tambon administrative organization (TAO).