Trie-sur-Baïse (French pronunciation: [tʁi syʁ ba.iz]; Occitan: Tria de Baïsa) is a commune in the Hautes-Pyrénées department in south-western France.

Trie-sur-Baïse is a commune of the Pays des Coteaux, an administrative area that includes Tournay, Castelnau-Magnoac, Pouyastruc and Galan.

The royal fortified town of Trie-sur-Baïse, the new Bastide, was founded in 1323 under a contract of a paréage signed by Jean de Trie, Seneschal of Toulouse and representative of the King, the seigneur of Bernard Duffort Manas, the seigneur of Puydarrieux Gerald of Esparros and a representative of the abbey Escaladieu, Father Roger Mauleon.

From December to February, the special "marché au gras" (goose and duck produce) takes place on Sundays.

On 26 July 2018, stage 18 of the Tour de France departed from Trie-sur-Baïse, with the route taking the professional cyclists to the finish in Pau.

The festival, called "La Grande Pourcailhade", was based around the theme of the pig and was traditionally held at the beginning of August.

Each year, on July 13 and August 13, night markets with fireworks, music and dancing are held from 7 pm onwards on the town square.

At the end of July, an antique fair is organised where one can buy, sell or simply admire curios, pieces of furniture and artefacts.