Marino Sanudo (or Sanuto) Torsello (c. 1270 – 1343) was a Venetian statesman and geographer. He is best known for his efforts to instigate a new crusade to the Holy Land. This lifelong task resulted in his book, 'Liber Secretorum Fidelium Crucis (Book of Secrets for True Crusaders) which would be supplented by an array of the earliest surviving portolan charts of the Mediterranean coast and the Black Sea, executed by Pietro Vesconte. Sanudo was born to an aristocratic trading family in Venice around 1270; his father was a member of the Venetian Senate. In his youth Sanuto traveled broadly, visiting in time Acre, Greece, Romania, Palestine, Egypt, Armenia, Cyprus and Rhodes. He would eventually join the entourage of the Doge of Venice; after 1305 he attended Cardinal Riccardo Petroni in Rome.

He was a vigorous correspondent, particularly with travelers whose reach had extended beyond his own.

Perhaps related to his early experiences in Acre - which fell rapidly to Muslim forces shortly after his visit there - Sanuto was a lifelong advocate of a crusade to capture the Holy Lands for the west. While he was certainly not alone among such instigators, his emphasis on strategy, practical financial backing, and detailed modern cartography set his proposals apart. His long term approach - with a preparatory blockade of and capture of Egypt to secure the invasion's flank - was never implemented. Nevertheless his book, often revised and updated, would find its way into the hands of not only the Pope but also King Charles IV of France. At least eleven manuscript copies are known to survive. Its complement of maps by Vesconte are the earliest medeival maps intended for military purposes.