Which 1998 Nintendo game was the first in The Legend of Zelda series to use a fully 3D world?

The Legend of Zelda: Ocarina of Time was the first game in the series to use a fully 3D world.

Nintendo released Ocarina of Time for the Nintendo 64 in Japan in November 1998, followed by North America and Europe in December 1998. It moved the series from overhead or side-view presentation into a navigable three-dimensional environment, while retaining exploration, dungeons, equipment, and puzzle solving.

The game introduced or popularized several important 3D design techniques. Its Z-targeting system helped players aim at enemies and interact with objects in a 3D space. The story also divided Link's adventure between childhood and adulthood, with the Master Sword creating a major time transition.

Earlier Zelda games used perspective tricks and multiple viewpoints, but they did not present the entire playable world as a continuous 3D environment. Majora's Mask followed in 2000 and reused many of the same technical foundations.