  Several scenarios were suggested for the origins of gravitational-wave (GW)
sources from mergers of stellar binary black holes (BBHs). Here we propose a
novel origin through catalyzed formation of GW-sources from ultra-wide binaries
in the field. Such binaries experience perturbations from random stellar
fly-bys which excite their eccentricities. Once a wide-binary is driven to a
sufficiently small peri-center approach, GW-emission becomes significant, and
the binary inspirals and merges. We derive an analytic model and verify it with
numerical calculation to compute the merger rate to be $\sim10{\rm \times
f_{wide}\,{\rm Gpc}^{-3}yr^{-1}}$ ($f_{{\rm wide}}$ is the fraction of wide
BH-binaries), which is comparable to the observationally inferred rate. The
observational signatures from this channel include spin-orbit misalignment;
preference for high mass-ratio BBH; preference for high velocity-dispersion
host-galaxies; and a uniform delay-time distribution.
