Which Pokémon League did Ash win first in the animated series?

Ash first won the Alola League in the Pokémon animated series.

Ash became the inaugural champion of the Alola League during Pokémon the Series: Sun & Moon. In the final, he defeated Gladion, fulfilling a long-running goal after competing in several earlier regional leagues.

The victory occurred in the Manalo Conference, the tournament that served as Alola’s Pokémon League competition. It marked Ash’s first regional Pokémon League championship in the main television anime after many earlier attempts.

The result is sometimes confused with Ash’s later World Coronation Series triumph. The Alola League victory came first, while the later Masters Eight tournament established Ash as the overall World Champion.