Buffalo buffalo buffalo buffalo buffalo Buffalo buffalo buffalo.
Short answer, yes, it's grammatically correct.
Tell me what it really says, though.
Here's the meaning, hidden, though:
The sentence means that large hairy oxen from a city in New York confuse large hairy oxen, and those confused oxen in turn confuse the oxen from New York. The buffalo from Buffalo confuse other buffalo, and those buffalo confuse the buffalo from Buffalo, New York.