Frà Giovanni Battista Tommasi (Cortona, 6 October 1731 – Catania, 13 June 1805) was an Italian nobleman and 73rd[citation needed] Prince and Grand Master of the Order of Malta.

He was born in the Kingdom of Naples and entered the Knights Hospitaller whilst still young, being sent to Malta aged 12 as a page of honour to Grand Master Emmanuel Pinto.

In the meantime the British had captured Malta and the Allied nations had agreed to re-establish the order, still dispersed across Europe and Russia and so unable to gather for a general assembly.

Straight after his appointment Tommasi sent the commander de Bussy to Malta to demand the British evacuate the island in line with article 10 of the treaty of Amiens and hand over the government palace in the fort at Valletta.

The Augustinian convent was put at their disposal while Tommasi himself lived in a neighbouring palace, where he died on 13 June 1805 aged 74, after having named bailli Innico Maria Guevara-Suardo lieutenant of the order in his place.