  We study how well the mass of the graviton can be constrained from
gravitational-wave (GW) observations of coalescing binary black holes. Whereas
the previous investigations employed post-Newtonian (PN) templates describing
only the inspiral part of the signal, the recent progress in analytical and
numerical relativity has provided analytical waveform templates coherently
describing the inspiral-merger-ringdown (IMR) signals. We show that a search
for binary black holes employing IMR templates will be able to constrain the
mass of the graviton much more accurately (about an order of magnitude) than a
search employing PN templates. The best expected bound from GW observatories
(lambda_g > 7.8 x 10^13 km from Adv. LIGO, lambda_g > 7.1 x 10^14 km from
Einstein Telescope, and lambda_g > 5.9 x 10^17 km from LISA) are several
orders-of-magnitude better than the best available model-independent bound
(lambda_g > 2.8 x 10^12 km, from Solar system tests). Most importantly, GW
observations will provide the first constraints from the highly dynamical,
strong-field regime of gravity.
