Methylammonium halides are organic halides with a formula of CH₃NH₃X, where X is Cl, Br or I. Generally they are white or light colored powders. They are used primarily to prepare light absorbing semiconductors for perovskite solar cells.

The primary application for these compounds is as a component of perovskite (structure) crystalline solar cells. The iodide is the most commonly used. When complexed with other metallic iodides such as tin iodide or lead iodide it can be used as a light gathering compound in place of naturally occurring organic dyes, providing excellent bandgap and charge mobility. Other methylammonium halides such as the chloride and bromide can be used instead of, or as minor substituents to, methylammonium iodide, providing the ability to tune the absorption, conductivity, and apparent bandgap. Magnetic ion doping like manganese results in a magnetic photoconductive material which opens avenues for magneto-optical data storage based on this material.

These compounds are usually prepared by combining equimolar amounts of methylamine with the appropriate halide acid. For instance methylammonium iodide is prepared by combining methylamine and hydrogen iodide at 0 °C for 120 minutes followed by evaporation at 60 °C, yielding crystals of methylammonium iodide.

These compounds' crystallography has been the subject of much investigation. J.S. Hendricks published an early paper on them in 1928. Methylammonium chloride was investigated again in 1946 and methylammonium bromide in 1961.

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