  We prove that Gromov's ellipticity condition $\mathrm{Ell}_1$ characterizes
Oka manifolds. This characterization gives another proof of the fact that
subellipticity implies the Oka property, and affirmative answers to Gromov's
conjectures. As another application, we establish the localization principle
for Oka manifolds, which gives new examples of Oka manifolds. In the appendix,
it is also shown that the Oka property is not a bimeromorphic invariant.
