Bertrand de Saint-Martin (died March 28 or 29, 1278) was a French cardinal.
He entered the Order of Benedictines and by 1238 was dean of the abbey of Saint-André de Villeneuve at Avignon. In 1248 he was elected bishop of Fréjus. In 1264 he was transferred to the see of Avignon, and in 1266 to the metropolitan see of Arles. Pope Gregory X created him Cardinal-Bishop of Sabina on June 3, 1273. He participated in the Second Council of Lyon (1274). His name appears among signatories of the papal bulls between March 7, 1274 and March 23, 1275. He participated in the three papal conclaves in 1276. He became dean of the Sacred College of Cardinals in September 1276, as the only cardinal-bishop in the College at that time.
For a long time it was thought that he died during the Second Council of Lyon in 1274 or in 1275, and shortly thereafter was succeeded in the see of Sabina by Giovanni Visconti, nephew of Gregory X. However, modern research has established that cardinal Giovanni Visconti never existed, while Bertrand is attested in the papal documents until the pontificate of John XXI (1276–77)[1]. His death has been registered in the contemporary necrologies under March 28 or March 29. The most probable year of his death seems to be 1278, because contemporary sources mention him as participant in the papal election, 1277 and in the first consistory of Pope Nicholas III on March 12, 1278 no new cardinal-bishop of Sabina had been appointed to replace him.[2]