"Jestem najlepszy!"

Translation: I am the best!

[tomboysquirrel]

Reminds me of the 2NE1 song!

[DorothyRoholt]

Does a female speaker say "Jestem najlepsza."?

[JerryMcCarthy99]

I believe "najlepszy" works like a standard adjective, and https://en.wiktionary.org/wiki/najlepszy and 'show' the declension indeed confirms it.

[agutek66]

Yes

[Kendra800150]

I would accept "I am best" without "the".

[Jellei]

OK, added.