UTBS 365 is a trail running series held in Cazorla, Jaen, Andalusia, Spain, featuring routes within the Sierras de Cazorla, Segura y Las Villas natural park. The primary event is the Ultra Bosques del Sur, a race just under 100 km. A 50 km option is available with the Maraton Bosques del Sur, and the broader 365 format also offers 25 km, 12 km, and 4 km routes. The standard event aligns with the UTMB Index, whereas the 365 version allows participants to complete a chosen route independently at any time during the calendar year.
The 365 concept is its unique element: runners may run their selected route multiple times, aiming to improve their personal best, and are included in a running leaderboard throughout the year. These self-navigated routes are not marked, making the use of a GPS track essential. At the year's conclusion, the top three finishers in each category are awarded diplomas, and the winner of each distance receives a prize and trophy.