Astrometry as a technique has so far proved of limited utility when employed as either a follow-up tool or to independently search for planetary-mass companions around stars in the solar neighborhood. However, the situation is bound to change soon. In this chapter, a brief overview is provided of past and present efforts to detect planets via milli-arcsecond (mas) astrometry, with a special focus on the legacy of the Hipparcos mission. The focus is next shifted on the Gaia mission that is poised to become a game changer in the field of exoplanets by unleashing for the first time the power of micro-arcsecond (μas) astrometry. First, the mission status and operations are briefly described. Next, some of the relevant technical issues are presented, which are associated with the precise and accurate determination of astrometric orbits of planetary systems using Gaia data. Then, the Gaia planet-finding capabilities are presented and discussed, and a brief summary is provided of the impact of Gaia in the exoplanet field obtained with the publication of the first two major data releases, Gaia DR2 and DR3. Finally, Gaia astrometry put in context, illustrating its potential for crucial contributions to exoplanetary science in synergy with other indirect and direct methods for the detection and characterization of planetary systems.