The 500 Hats of Bartholomew Cubbins is a children's book, written and illustrated by Theodor Geisel under the pen name Dr. Seuss and published by Vanguard Press in 1938.

One day, Bartholomew goes into the town to sell some cranberries, when he comes across King Derwin, the ruler of the Kongdom of Didd, riding through a street.

The royal hatter runs away in terror; the King’s wise men only nibble their beards in awe; the King's young nephew, Wilfred, fails to shoot the hats off with arrows; a great bowman similarly fails with a longbow; and the royal magicians attempt to curse the hat away, but claim that their spell will only work in "Ten Short Years".

Ultimately, the 500th hat is revealed as the greatest, studded with a massive gem and feathers from rare birds, although Bartholomew seems unaware of the fact.

The New York Times reviewer called the book "a lovely bit of tomfoolery which keeps up the suspense and surprise until the end".

[2] Booklist, which had criticized Geisel's previous book, And to Think That I Saw It on Mulberry Street, for containing only enough material for one comic strip, praised The 500 Hats as "a brand-new idea, developed into a complete tale, not too long, not too short, just right.