Gisa (also spelt Giso) was Bishop of Wells from 1060 to 1088.

Gisa was born in Lorraine, and was among a number of foreign churchmen brought to England by Edward the Confessor. At first he held the position of king's chaplain, but in January 1060 he was elected to become Bishop of Wells. Pope Nicholas II consecrated him on 1061-04-15 in Rome.

On his arrival in the see he found the church there was in dire need, with the canons having to beg for bread. He constructed cloisters to the north of Wells Cathedral and communal buildings to the south for the canons. Before this time canons in England lived separately from one another and the cathedral, but Gisa introduced the Rule of Chrodegang which meant they had to live communally at the church they served. Though the rule was popular in Europe it did not take hold in England and was later reversed.

Gisa obtained land grants for the upkeep of the church and canons from Edward and later Harold Godwinson and William the Bastard. He is mentioned many times in the Domesday Book as the holder of land for the see, and was notorious for acquiring land throughout his bishopric.

In 1080, Adelard of Bath was born to Fastrad, a member of Gisa's household.