Gerard (c. 1040 – September 3, 1120), variously surnamed Tum, Tune, Tenque or Thom, was the founder of the Order of the Knights of St. John of Jerusalem, or the Knights Hospitaller.

He was born possibly at Amalfi, or according to other accounts Martigues in Provence, while one authority even names the Chateau d'Avesnes in Hainaut. Either as a soldier or a merchant, he found his way to Jerusalem, where a hospice had for some time existed for the convenience of those who wished to visit the Christian holy places. Of this institution Gerard became guardian or provost at a date not later than 1100, and here he organized that religious order of St John which received papal recognition from Paschal II in 1113, by the bull Geraudo institutori ac praeposito Hirosolimitani Xenodochii. It was renewed and confirmed by Calixtus II shortly before the death of Gerard in 1120.