(145451) 2005 RM43 (provisional designation 2005 RM43) is a trans-Neptunian object that resides in the scattered disc region beyond the Kuiper belt.

[8][10] Based on an absolute magnitude of 4.4, the body's diameter could be anywhere in the range of 350 to 800 kilometres (km), depending on its albedo, the surface reflectivity of the object.

[2] Brown estimates a diameter of 524 km, based on an absolute magnitude of 4.8 and an assumed albedo of 0.08.

[3] Observations of the February occultation yielded a single chord length of 456 km (283 mi).

[12] Observations of the December occultation yielded two positive chords, which suggest an approximate diameter of 644 km (400 mi) for 2005 RM43.