The 2003–04 ECHL season was the 16th season of the ECHL. This was the first season that the league would be known as only the ECHL instead of East Coast Hockey League after the absorption of the former West Coast Hockey League teams. The Brabham Cup regular season champions were the San Diego Gulls and the Kelly Cup playoff champions were the Idaho Steelheads.

This season brought a major change in the ECHL as the Board of Governors approved membership applications from the Anchorage Aces, the Bakersfield Condors, the Fresno Falcons, the Idaho Steelheads, the Las Vegas Wranglers, the Long Beach Ice Dogs and the San Diego Gulls from the recently defunct West Coast Hockey League. In a change reflective of the nationwide presence, the East Coast Hockey League changed its name to simply ECHL on May 19, 2003.

During the 2003 off-season, the Richmond Renegades, Arkansas RiverBlades, Jackson Bandits, Baton Rouge Kingfish, and Lexington Men O' War all ceased operations.

In addition to the former WCHL teams, the league also added two reactivated franchises in the Gwinnett Gladiators (formerly the Mobile Mysticks) and Texas Wildcatters (formerly the Huntington Blizzard).

The ECHL All-Star Game was held at Carver Arena in Peoria, Illinois, and was hosted by the Peoria Rivermen. The Eastern Conference All-Stars defeated the Western Conference All-Stars 7–6, with Peoria's Randy Rowe named Most Valuable Player.

• List of ECHL seasons
• 2003 in sports
• 2004 in sports