Phon Phisai (Thai: โพนพิสัย, pronounced [pʰōːn pʰíʔ.sǎj]; Northeastern Thai: โพนพิสัย, pronounced [pʰo᷇ːn pʰìʔ.sǎj]) is a district (amphoe) in Nong Khai province, northeastern Thailand.

Neighboring districts are (from the east clockwise) Rattanawapi and Fao Rai of Nong Khai Province; Ban Dung, Sang Khom, and Phen of Udon Thani province; and Mueang Nong Khai of Nong Khai.

To the north across the Mekong River are the Laotian Vientiane Prefecture and Bolikhamxai province.

The district is divided into 11 sub-districts (tambons), which are further subdivided into 151 villages (mubans).

Missing numbers are tambon which now form the districts Fao Rai and Rattanawapi.