While the idea that the Earth was a sphere was prevalent in ancient Greece, Ferdinand Magellan is credited with the first recorded circumnavigation of the globe.

Here's why it's not a straightforward answer:

* Ancient Greeks: Philosophers like Pythagoras and Aristotle theorized that the Earth was a sphere, based on observations like the curvature of the Earth's shadow on the moon during eclipses. However, they didn't actually circumnavigate the globe to prove it.

* Magellan's Expedition: Magellan's expedition, which began in 1519, aimed to find a westward route to the Spice Islands. Though Magellan himself was killed during the journey, his crew completed the voyage in 1522, providing the first verifiable proof of the Earth's spherical shape.

Therefore, while the ancient Greeks proposed the idea, Magellan's expedition provided the first concrete evidence of the Earth's spherical shape.