Bishop Guertin (BG) is a college preparatory independent private Roman Catholic high school in Nashua, New Hampshire.

Named for Bishop George Albert Guertin (1869–1931), it was founded by the Brothers of the Sacred Heart in 1963.

Guertin students are able to take courses in these departments at the "College Preparatory", "Honors", or "Advanced Placement" level.

While Bishop Guertin is one of the smaller Division I schools in New Hampshire, its ability to draw students from a wide geographic area in southern New Hampshire and northeastern Massachusetts enables it to be highly competitive in its division.

For decades, Bishop Guertin played their crosstown public school rival, the Nashua Purple Panthers in the Turkey Bowl on Thanksgiving.

In 2004, Nashua High School was split into the Panthers of South and the Titans of North, and Bishop Guertin no longer played in the Thanksgiving Day game.

Donald Tardif and Mrs. Maureen Deblasio initiated a mission trip to Zambia to visit and do community work at a high school run by the Brothers of the Sacred Heart of Eastern and Southern Africa.