The O'Reilly Open Source Convention (OSCON) was an American annual convention for the discussion of free and open-source software.

It was organized by publisher O'Reilly Media and was held each summer, mostly in Portland, Oregon, from 1999 to 2019.

OSCON grew out of The Perl Conference, but the amount of Perl content continued to decline each year.

The first Perl Conference took place in 1997.

The first OSCON was held in 1999.