Here’s a clean top 10 list of the fastest Pokémon by base Speed stat, using the standard ranking most fans refer to. Regieleki is #1, and the list below follows the modern all-time speed leaders.

Rank Pokémon Base Speed
1Regieleki200
2Deoxys (Speed Forme)180
3Ninjask160
4Pheromosa151
5Electrode150
6Mega Aerodactyl150
7Mega Alakazam150
8Shadow Rider Calyrex150
9Zacian148
10Accelgor145

Notes

This kind of ranking is based on base stats, not in-battle speed after items, boosts, or abilities. Different sources may shift the lower end a bit because of ties among Pokémon with the same base Speed, but the top names stay very consistent.

Quick context

If you want the list for only non-legendary Pokémon, or only fully evolved Pokémon, the ranking changes a lot. For example, Ninjask, Accelgor, and Electrode become even more prominent in those narrower lists.