Justin Frankel (born 1978) is an American computer programmer best known for his work on the Winamp media player application and for inventing the Gnutella peer-to-peer network.

After graduating high school with a 3.9 GPA, he attended the University of Utah in 1996, where he majored in computer science, but dropped out after two quarters.

Since many people had sent in the $10 donation suggested in return for using the program, Frankel earned tens of thousands of dollars a month.

In June 1999 AOL simultaneously acquired Nullsoft and Spinner.com in a combined purchase worth approximately $400 million.

It also did not have the single point of failure that Napster had: centralized servers that indexed where all the shared content was stored.

Some of Frankel's current projects in development are a programmable effects processor called Jesusonic and a piece of software named NINJAM which allows several musicians to make music together via the Internet.

Under his new company, Cockos, he has been developing REAPER, a digital audio workstation for Microsoft Windows, MacOS, and Linux.