Metrolink's 91 line (sometimes called the Riverside-Fullerton Line) goes from Downtown Los Angeles to Riverside paralleling the very busy California State Freeway 91. The 91 line runs 5 days a week with peak hour and limited midday service. The line mostly shares stations with the Orange County Line and Inland Empire-Orange County Line(IEOC) At Riveride-Downtown station it connects with the Riverside Line

The 91 Line has been operating to Riverside since May 2002 providing 9 weekday trips to and from Los Angeles. A few peak-hour trains run to and from San Bernardino.

There are 8 stations that serve the 91 line.

1. Union Station

2. Commerce (Los Angeles County)

3. Norwalk/Santa Fe Springs

4. Fullerton

5. West Corona

6. North Main Corona

7. Riverside-La Sierra

8. Riverside-Downtown