  We study for the first time the possibility of probing long-range fifth
forces utilizing asteroid astrometric data, via the fifth force-induced orbital
precession. We examine nine Near-Earth Object (NEO) asteroids whose orbital
trajectories are accurately determined via optical and radar astrometry.
Focusing on a Yukawa-type potential mediated by a new gauge field (dark photon)
or a baryon-coupled scalar, we estimate the sensitivity reach for the fifth
force coupling strength and mediator mass in the mass range $m \simeq
(10^{-21}-10^{-15})\,{\rm eV}$, near the ``fuzzy'' dark matter region. Our
estimated sensitivity is comparable to leading limits from equivalence
principle tests, potentially exceeding these in a specific mass range.
Furthermore, we set new constraints on Yukawa gravity. The fifth force-induced
precession increases with the orbital semi-major axis in the limit of a small
mass $m$, motivating the study of objects further away from the Sun. We discuss
future prospects for extending our study to more than a million asteroids,
including NEOs, main-belt asteroids, Hildas, and Jupiter Trojans, as well as
trans-Neptunian objects and exoplanets.
