Maybe this is cheating, but there are a few lists on Wikipedia that give dozens of answers:
gives: Beer–Lambert law, Biot–Savart law, Cauchy–Riemann equations, Cayley–Hamilton theorem, Church–Turing thesis, Law of Charles and Gay-Lussac, Curie–Weiss law, De Bruijn–Erdős theorem, Erdős–Anning theorem, Erdős–Beck theorem, Erdős–Gallai theorem, Erdős–Kac theorem, Erdős–Nagy theorem, ok I’m getting tired of Erdős, but there’s a lot more.
Then this one gives more: List of scientific equations named after people - Wikipedia
Adams–Williamson equation, Allen–Cahn equation, Ashkin–Teller model, Batchelor–Chandrasekhar equation, Benjamin–Ono equation, Birch–Murnaghan equation of state, Birkhoff–Rott equation, Blaney–Criddle equation, Borda–Carnot equation, Buckley–Leverett equation, Cahn–Hilliard equation, Callan–Symanzik equation, Callendar–Van Dusen equation, … I didn’t even get through the C’s on that page.
And then there’s List of scientific constants named after people - Wikipedia which gives a few: Copeland–Erdős constant, Embree–Trefethen constant, Erdős–Borwein constant, Euler–Mascheroni constant, Landau–Ramanujan constant, Meissel–Mertens constant, Ramanujan–Soldner constant, Sackur–Tetrode constant, Stefan–Boltzmann constant. I think I got all of them from that page.
And then there’s this page, List of equations - Wikipedia which overlaps a lot with the others, but probably has some new ones.
None of them seem to mention my favorite, the Banach-Tarski paradox.