Reniero Zeno (Venetian: Renieri Zen) (died 7 July 1268) was the 45th Doge of Venice, reigning from 1 January 1253 until his death in 1268.

The first references to Reniero Zeno in historical sources describe him as a diplomat in France and Italy, where he was excommunicated for having pushed Bologna to avoid paying tributes to the Papal States.

In 1240 he helped Doge Jacopo Tiepolo during the siege of Ferrara, in 1242 put down a revolt in Zara and in 1244 he was named capitano generale da Mar (fleet commander) of the Republic of Venice.

When the future Doge Lorenzo Tiepolo destroyed the Genoese fleet in 1257, Genoa allied with Michael VIII Palaeologus, who in 1261 captured Constantinople, putting an end to the Latin Empire and awarding Genoans the privileges formerly held by Venetians.

In 1268 a five-year truce was signed with Byzantine Empire which restored to the Venetians many of their former priviliegies, establishing an uneasy balance between the two maritime republics, allowing them to compete freely in the Levant.