  Stellar multiplicity is among the oldest and richest problems in
astrophysics. Binary stars are a cornerstone of stellar mass and radius
measurements that underpin modern stellar evolutionary models. Binaries are the
progenitors of many of the most interesting and exotic astrophysical phenomena,
ranging from type Ia supernovae to gamma ray bursts, hypervelocity stars, and
most detectable stellar black holes. They are also ubiquitous, accounting for
about half of all stars in the Universe. In the era of gravitational waves,
wide-field surveys, and open-source stellar models, binaries are coming back
stronger than a nineties trend. Much of the progress in the last decade has
been enabled by the Gaia mission, which provides high-precision astrometry for
more than a billion stars in the Milky Way. The Gaia data probe a wider range
of binary separations and mass ratios than most previous surveys, enabling both
an improved binary population census and discovery of rare objects. I summarize
recent results in the study of binary stars brought about by Gaia, focusing in
particular on developments related to wide ($a \gtrsim 100$ au) binaries,
evidence of binarity from astrometric noise and proper motion anomaly,
astrometric and radial velocity orbits from Gaia DR3, and binaries containing
non-accreting compact objects. Limitations of the Gaia data, the importance of
ground-based follow-up, and anticipated improvements with Gaia DR4 are also
discussed.
