(26375) 1999 DE9 (also written (26375) 1999 DE9) is a trans-Neptunian object. Light-curve-amplitude analysis shows only small deviations, suggesting (26375) 1999 DE9 is a spheroid with small albedo spots. Measurements by the Spitzer Space Telescope estimate that it is 461 ± 45 km in diameter. It was discovered in 1999 by Chad Trujillo and Jane X. Luu. It is possibly a dwarf planet.