(374158) 2004 UL

 is a sub-kilometer asteroid on an outstandingly eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. The object is known for having the second-smallest perihelion of any known asteroid, after.

It was discovered on 18 October 2004 by the Lincoln Near-Earth Asteroid Research (LINEAR) at Lincoln Lab's ETS near Socorro, New Mexico.

Orbit and classification
This Apollo asteroid orbits the Sun at a distance of 0.09–2.44 AU once every 17 months (521 days; semi-major axis of 1.27 AU). Its orbit has an outstandingly high eccentricity of 0.93 and an inclination of 24° with respect to the ecliptic.

Due to its orbit, it is also a Mercury-crosser, Venus-crosser and Mars-crosser. It has an Earth minimum orbital intersection distance of 0.0182 AU, which translates into 7.1 lunar distances.

Physical characteristics
is an assumed stony S-type asteroid.

In October 2014, a rotational lightcurve for this asteroid was obtained from photometric observations by American astronomer Brian Warner at the CS3–Palmer Divide Station (U82) in Landers, California. It gave a longer-than average rotation period of $38 h$ hours (most minor planets take 2–20 hours to complete a full rotation) with a high brightness variation of 1.2 magnitude, indicating a non-spheroidal shape (U=2).

Based on a generic magnitude-to-diameter conversion, measures between 0.5 and 1.2 kilometers. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 0.516 kilometers with an absolute magnitude of 18.8.

Numbering and naming
This minor planet was numbered by the Minor Planet Center on 18 October 2013 (M.P.C. 85347). As of 2018, it has not been named.