Since the first report of their isolation in 2007, magnesium(I) dimers have transitioned from being chemical curiosities to versatile reducing agents that are used by an ever-increasing number of synthetic chemists. Magnesium(I) dimers have a unique combination of advantageous properties that sees them used in the syntheses of new, and often applicable, compound types that are impossible or difficult to access using conventional reductants. This Perspective describes the synthesis and properties of these dimers, and provides notable examples of their application in organic and inorganic synthesis. Magnesium(I) dimers, especially complexes of β-diketiminates, may now be viewed as widely applicable, quasi-universal reducing agents with a promising future in synthetic chemistry. It is hoped that the reader will develop a familiarity with these reagents, such that the complexes can be successfully used in many synthetic programmes.