He was born to a noble family in Maastricht (in modern-day Netherlands). When his spiritual father Bishop Theodard was killed in 671, St Lambert was elected Bishop of Maastricht despite his youth. He was loved by his flock for his holiness, ascetic labors and almsgiving, but was driven from his see in 675 after his patron King Childeric II was assasinated. He withdrew to the Monastery of Stavelot where he lived for seven years as one of the brethren, claiming no privileges despite his office. Once, getting up to pray during the night, he accidentally disturbed the monastic silence. The Abbot called out for whoever was responsible to do penance by standing barefoot in the snow before a cross outside the monastery church. In the morning the Abbot was dismayed to see the Bishop standing barefoot, covered with snow, before the cross, his face shining. The Abbot sought to apologize, but Lambert replied that he was honored to serve God like the Apostles, in cold and nakedness.

When King Pepin of Heristal took power in 681, he restored Lambert to his see, despite the Saint's desire to remain in obscurity. The holy bishop renewed his pastoral labors with vigor, visiting the most distant parishes and preaching the Gospel to the pagans who still inhabited the area, despite danger and threats. But when King Pepin put away his wife and replaced her with his concubine Alpais, St Lambert was the only Bishop who dared to rebuke him. For this he incurred the wrath of Alpais, who ordered his death. His assassins carried out their evil commission, even though they found a cross shining above the humble dwelling where he was staying.

Saint Lambert is one of the best-loved Saints of the Netherlands and Belgium, where many parish churches are dedicated to him. His relics are now in the Belgian city of Liège.