Lake Sonoma 100K, 50K & TS Half

Join us in Healdsburg, California, on April 11th 2026 for the TERREX Lake Sonoma 100K, 50K, and Trail Sisters Half Marathon! We are excited to have adidas TERREX back as our presenting partner!

We are stoked to team up with Mountain Outpost to bring you full livestream coverage, athlete panels, interviews, and commentary from special guests!

Lake Sonoma 100K

The 100K course will start with a climb up Pritchett Peak with a water only stop at the top. Once you reach the summit you’ll head back down toward the Lake Sonoma Visitors Center and then up to the hill to South Lake Trailhead where you’ll embark on an out and back of the original old school LS course and then back down the hill to the finish. It’s the same great Lake Sonoma Relentless experience, only this time with a big climb to kick it all off!

Lake Sonoma 50K

It’s not worth it unless you have to work for it! The 50k start is located in the green space next to the Lake Sonoma Visitor Center (you can’t miss it). After a short road section to get the field spread out  the course then continues onto beautiful rolling single track trails. You will continue past South Lake, Island View, Warm Springs Creek, Wulfow, Liberty Glen and the Bummer aid stations, finally crossing the scenic lake bridge. Remember to save some juice for the last few miles, as you have a screaming downhill towards the finish. The race starts at 7:30am.

Don’t forget to enjoy the views! … and be sure to take a dip in the water to cool off. (but don’t drink!)

Trail Sisters Women's Half Marathon

The Trail Sisters (TS) Half Marathon is a women’s only event. It was created to foster encouragement and camaraderie amongst all abilities and experience levels. This out and back course starts with steep trail ascent to South Lake Trailhead, but also provides a speedy descent to the finish. True to its label, you can expect relentless rolling hills that will challenge your mind and body. Lucky for you though, you will share the journey with a community of supportive Trail Sisters to help you through! You will have 4 and half hours to complete the half marathon course.

Come Celebrate!

Lake Sonoma isn’t just a race event, it’s a celebration. We always complete the weekend with a Celebration and Thank You event at Coyote Sonoma in Healdsburg, CA. Everyone involved with the event is invited to enjoy wine, charcuterie, and share stories from the weekend.

See you on that start line!

Gina & Justin

LS Race Directors