What is the name of the first track in the Mushroom Cup of Super Mario Kart?

The first track in the Mushroom Cup of Super Mario Kart is Mario Circuit 1.

Mario Circuit 1 opens the game’s Mushroom Cup and serves as an introductory circuit built around the familiar Mario-themed road setting. Its layout uses broad turns, pipe barriers, coins, item panels, and boost surfaces, giving new players an early chance to learn steering, drifting, item use, and the game’s five-lap race format.

The complete Mushroom Cup sequence is Mario Circuit 1, Donut Plains 1, Ghost Valley 1, Bowser Castle 1, and Mario Circuit 2. That order explains why several other answers can seem plausible: each listed alternative is also a real Super Mario Kart track, and Bowser Castle 1, Ghost Valley 1, and Donut Plains 1 all appear later in the same cup.

Super Mario Kart divides its Grand Prix into cups containing five tracks each. The original game has four cups and 20 unique Grand Prix tracks, with a fourth Special Cup unlocked through progression. Mario Circuit 1 also became notable beyond the original game because it was later remade as a retro course in Mario Kart DS.