Bais (French pronunciation: [bɛ]; Breton: Baez; Gallo: Baès) is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. The writer Anne de Tourville (1910–2004), winner of the 1951 Prix Femina, was born in Bais.

Historical population

Year	Pop.	±% p.a.
1968	2,095	—
1975	2,022	−0.51%
1982	1,913	−0.79%
1990	1,821	−0.61%
1999	1,928	+0.64%
2007	2,020	+0.58%
2012	2,152	+1.27%
2017	2,419	+2.37%
Source: INSEE

Inhabitants of Bais are called Baiséens in French.

Gallo-Roman remains have been discovered that date from the first century AD.

The church of Saint Mars was built primarily in the 16th century, with expansion in the 19th century. It is dedicated to Saint Mars, bishop of Nantes in the sixth century, who became a hermit in the neighboring village of Marsé.

• Communes of the Ille-et-Vilaine department

• Official website (in French)
• Cultural Heritage (in French)
• Mayors of Ille-et-Vilaine Association Archived 14 January 2012 at the Wayback Machine (in French)