I will present a review of the role of mergers in galaxy evolution, focusing primarily on observational evidence for the various ways in which mergers affect galaxies. In a Lambda CDM Universe, structure grows hierarchically with dark matter haloes growing by constant accretion of matter and through discrete merger events. Galaxies, which reside in larger dark matter haloes, merge together as a consequence of halo mergers. Hence, accurately constraining the merger history (as a function of mass, mass-ratio, epoch and environment) can provide powerful constraints to cosmology and/or the physics of galaxy formation. Additionally, there is a wealth of observational evidence to suggest that merger events can lead to enhanced star formation rates and star bursts, and can trigger or enhance active galactic nuclei (AGN). Mergers are particularly prevalent in the most luminous quasars and star bursts at high redshifts. Furthermore, the merging of rotationally supported disk-like galaxies can produce pressure supported spheroidal or elliptical galaxies, and as such has become a much favoured mechanism for governing morphological and kinematic evolution, at least for more massive galaxies. Mergers are also implicated in star formation quenching, either directly by exhausting gas reserves, or indirectly through triggering supernovae or AGN-feedback. I will end by reviewing the current state of the art in merger detection and analysis in large galaxy surveys (e.g., DES) and look at the prospects for the future with EUCLID and LSST. In conclusion, I will suggest that our understanding of galaxy mergers and their role in galaxy evolution is about to undergo a revolution, as we will routinely be able to identify millions of galaxy mergers across space and time.