Blue Goat's Backyard Marathons are small-field trail races held on Darling Causeway at Mount Victoria in the Blue Mountains, originating from the backyard of Blue Mountains Fitness' Tony Williams. The series typically includes distances from a 1 km kids race and 5 km dash up to 10.5 km, half marathon, 30 km, marathon, 50 km, and a Last One Standing endurance race. Entry numbers are limited to 200, and the event is eligible for UTMB Index points.
Most distances involve repeated 10.5 km laps, while the 5 km race and Last One Standing utilize a distinct 5 km loop on highly technical trail. The Last One Standing format has runners completing one loop each hour in an elimination style, progressively reducing the field until a single runner remains. The course features significant elevation gain, attracts an audience leaning towards ultra runners, and its results history, though limited, is demanding: only 76 finishers are documented across previous Last One Standing editions, with the longest winning distances varying between 84 km and 160 km.