Tolmin Castle (Slovene: Grad Tolmin, Italian: Castello di Tolmino, German: Bockstein, Tulmein), also known as the Castle on Kozlov Rob above Tolmin (Grad na Kozlovem Robu nad Tolminom), is a fortress ruin on the ridge of Kozlov Rob ('Billy-goat's Edge') above the town of Tolmin in southwestern Slovenia.