Yes, trekking in Upper Mustang requires a special permit due to its restricted status. There are two main permits needed: the Upper Mustang Trekking Permit and the Annapurna Conservation Area Permit (ACAP). The Upper Mustang Trekking Permit is quite costly compared to other trekking permits, reflecting the region's status as a protected area. The Upper Mustang Permit can only be obtained through registered trekking agencies in Nepal, and it's essential to apply well in advance. The ACAP is required as the trek falls within the Annapurna Conservation Area. Both permits help to regulate tourism and preserve the area's cultural and environmental integrity. Ensure that your trekking agency arranges these permits for you as part of your trek's logistics.