Stern is a Class IV rapid located at mile 4. 4 on the Tuolumne River below Lumsden, characterized by large boulders that block the river and create a narrow, technical chute.

At low summer flows, rafts must navigate a boat-width channel between the leftmost boulder and the left cliff wall, requiring precise maneuvering to avoid being turned sideways; at higher flows, multiple routes become available and the rapid becomes more manageable.

This rapid is considered one of the most feared on the river at low water but is generally runnable for experienced paddlers with proper technique.