Mirror Coat is learned by 24 species by level and 28 by egg

Effect, in PokéAPI's words

“Inflicts twice the damage the user received from the last special hit it took.”

Who learns it

51 species in all, 8 of 20 games shown

Scarlet and Violet: 34 species

Species	Method	Level
Magnezone	Level up	1
Arboliva	Level up	1
Glaceon	Level up	45
Tatsugiri	Level up	47
Dewpider	Level up	48
Voltorb	Level up	50
Electrode	Level up	58
Suicune	Level up	60
Araquanid	Level up	62
Sandy Shocks	Level up	70
Miraidon	Level up	70
Squirtle	Egg
Wartortle	Egg
Blastoise	Egg
Tentacool	Egg
Tentacruel	Egg
Girafarig	Egg
Mudkip	Egg
Marshtomp	Egg
Swampert	Egg
Spoink	Egg
Feebas	Egg
Milotic	Egg
Shellos	Egg
Snivy	Egg
Servine	Egg
Serperior	Egg
Gothita	Egg
Alomomola	Egg
Bergmite	Egg
Snom	Egg
Duraludon	Egg
Toedscool	Egg
Archaludon	Egg

Brilliant Diamond and Shining Pearl: 19 species

Species	Method	Level
Wobbuffet	Level up	Evolve, 1
Wynaut	Level up	1
Lopunny	Level up	1
Magnezone	Level up	1
Glaceon	Level up	45
Voltorb	Level up	48
Corsola	Level up	55
Electrode	Level up	58
Suicune	Level up	60
Squirtle	Egg
Tentacool	Egg
Girafarig	Egg
Mantine	Egg
Mudkip	Egg
Spoink	Egg
Lileep	Egg
Feebas	Egg
Shellos	Egg
Mantyke	Egg

Sword and Shield: 30 species

Species	Method	Level
Wobbuffet	Level up	Evolve, 1
Wynaut	Level up	1
Lopunny	Level up	1
Magnezone	Level up	1
Orbeetle	Level up	32
Vanillite	Level up	36
Mr. Rime	Level up	36
Vanillish	Level up	38
Vanilluxe	Level up	38
Glaceon	Level up	45
Dewpider	Level up	48
Corsola	Level up	55
Cursola	Level up	55
Suicune	Level up	60
Nihilego	Level up	60
Araquanid	Level up	62
Squirtle	Egg
Tentacool	Egg
Mantine	Egg
Mudkip	Egg
Lileep	Egg
Feebas	Egg
Shellos	Egg
Mantyke	Egg
Gothita	Egg
Amaura	Egg
Bergmite	Egg
Pyukumuku	Egg
Snom	Egg
Duraludon	Egg

Let's Go Pikachu and Let's Go Eevee: 4 species

Species	Method	Level
Tentacruel	Level up	1
Articuno	Level up	24
Voltorb	Level up	38
Electrode	Level up	48

Ultra Sun and Ultra Moon: 30 species

Species	Method	Level
Wobbuffet	Level up	1
Lopunny	Level up	1
Magnezone	Level up	1
Wynaut	Level up	15
Glaceon	Level up	33
Dewpider	Level up	40
Suicune	Level up	43
Nihilego	Level up	43
Vanillite	Level up	44
Corsola	Level up	45
Vanillish	Level up	47
Voltorb	Level up	48
Vanilluxe	Level up	50
Araquanid	Level up	50
Electrode	Level up	58
Squirtle	Egg
Tentacool	Egg
Girafarig	Egg
Mantine	Egg
Mudkip	Egg
Spoink	Egg
Lileep	Egg
Feebas	Egg
Shellos	Egg
Mantyke	Egg
Snivy	Egg
Gothita	Egg
Alomomola	Egg
Amaura	Egg
Bergmite	Egg

Sun and Moon: 30 species

Species	Method	Level
Wobbuffet	Level up	1
Lopunny	Level up	1
Magnezone	Level up	1
Wynaut	Level up	15
Glaceon	Level up	33
Dewpider	Level up	40
Suicune	Level up	43
Nihilego	Level up	43
Vanillite	Level up	44
Corsola	Level up	45
Vanillish	Level up	47
Voltorb	Level up	48
Vanilluxe	Level up	50
Araquanid	Level up	50
Electrode	Level up	58
Squirtle	Egg
Tentacool	Egg
Girafarig	Egg
Mantine	Egg
Mudkip	Egg
Spoink	Egg
Lileep	Egg
Feebas	Egg
Shellos	Egg
Mantyke	Egg
Snivy	Egg
Gothita	Egg
Alomomola	Egg
Amaura	Egg
Bergmite	Egg

Omega Ruby and Alpha Sapphire: 27 species

Species	Method	Level
Wobbuffet	Level up	1
Lopunny	Level up	1
Magnezone	Level up	1
Wynaut	Level up	15
Glaceon	Level up	33
Suicune	Level up	43
Vanillite	Level up	44
Corsola	Level up	45
Vanillish	Level up	47
Voltorb	Level up	48
Vanilluxe	Level up	50
Electrode	Level up	58
Squirtle	Egg
Tentacool	Egg
Girafarig	Egg
Mantine	Egg
Mudkip	Egg
Spoink	Egg
Lileep	Egg
Feebas	Egg
Shellos	Egg
Mantyke	Egg
Snivy	Egg
Gothita	Egg
Alomomola	Egg
Amaura	Egg
Bergmite	Egg

X and Y: 27 species

Species	Method	Level
Wobbuffet	Level up	1
Lopunny	Level up	1
Magnezone	Level up	1
Wynaut	Level up	15
Glaceon	Level up	33
Suicune	Level up	43
Vanillite	Level up	44
Corsola	Level up	45
Vanillish	Level up	47
Voltorb	Level up	50
Vanilluxe	Level up	50
Electrode	Level up	62
Squirtle	Egg
Tentacool	Egg
Girafarig	Egg
Mantine	Egg
Mudkip	Egg
Spoink	Egg
Lileep	Egg
Feebas	Egg
Shellos	Egg
Mantyke	Egg
Snivy	Egg
Gothita	Egg
Alomomola	Egg
Amaura	Egg
Bergmite	Egg