P400 may refer to:

• P400 class patrol vessel
• P-400, the export model of P-39 Airacobra fighter

• Sultan of Hobyo
• Sultan of Jambi
• Sultan of Majeerteen
• Sultan of Mogadishu
• Sultan of Muscat and Oman
• Sultan of Negeri Sembilan
• Sultan of Perlis
• Sultan of Riau-Lingga
• Sultan of Tessaoua
• Sultan of the Fur
• Sultan of the Maldive Islands
• Sultan of Tidore
• Sultan of Tlemcen
• Sultan of Trengganu
• Sultanol
• Sultan Omar Ali Saifuddien Mosque
• Sultan Paduka Pahala
• Sultan Palace
• Sultan Palace (disambiguation)
• Sultan Palembang
• Sultanpally
• Sultanpally, Ranga Reddy district
• Sultan Pasha Atrash
• Sultanpet
• Sultanpet Block