Isaac Kaufmann Funk (1839-1912) was a United States editor, lexicographer, publisher, and spelling reformer. He co-founded the publishing firm of Funk and Wagnalls.

Perhaps Funk's most important achievement was his The Standard Dictionary of the English Language, published in 1893. He worked with a team of more than 740 people. His aim was to provide essential information thoroughly and simply at the same time. In order to achieve this he placed current meanings first, archaic meanings second, and etymologies last.