The Source was the name of an early on-line service. One of the first on-line services to be oriented toward and available to the general public, The Source was in operation from 1978 to 1989, when it was purchased by rival Compuserve Information Services and discontinued. At its peak, it had 80,000 members. During much of its existence, it charged a startup fee of about $100 and hourly usage rates on the order of $10 per hour. It provided news sources, weather, stock quotations, a shopping service, electronic mail, various databases, online text of magazines, and airline schedules. It also had a newsgroup-like facility known as PARTICIPATE (or PARTI), which was developed by Participation Systems of Winchester, Massachusetts. PARTICIPATE provided what it called "many to many" communications, or computer conferencing.

Intended for use with 300 bit/s and 1200 bit/s dial-up telephone connections, The Source was text-based for most of its existence.