He is the oldest known living terrestrial animal in the world.
And there was me thinking I was getting old.
He has his own Wikipedia page:
Jonathan (hatched c. 1832) is a Seychelles giant tortoise (Aldabrachelys gigantea hololissa), a subspecies of the Aldabra giant tortoise (Aldabrachelys gigantea), and the oldest known living terrestrial animal in the world. Jonathan resides on the island of Saint Helena, a British Overseas Territory in the South Atlantic Ocean.
The tweet I linked to above says “happy birthday” to Jonathan, but they don’t know exactly when he was born. He could be even older.