The monohalomethanes are organic compounds in which a hydrogen atom in methane is replaced by a halogen. They belong to the haloalkanes or to the subgroup of halomethanes.

Structural formula
Name	Fluoromethane Methyl fluoride	Chloromethane Methyl chloride	Bromomethane Methyl bromide	Iodomethane Methyl iodide
Melting point	−137,8 °C[1]	−97,4 °C[2]	−93,7 °C[3]	−66 °C[4]
Boiling point	−78,4 °C[1]	−23,8 °C[2]	4,0 °C[3]	42 °C[4]
Space-filling model

The four common^{[lower-alpha 1]} members are fluoromethane, chloromethane, bromomethane and iodomethane.

Historical name for this group is methyl halides; it's still widely used. The compounds of this class are often described as CH₃X or MeX (X - any halogen, Me - methyl group).

There are analogs with more than one hydrogen atom in methane is replaced by a halogen:

• Dihalomethane, CH₂X₂, two hydrogen atoms replaced
• Trihalomethane, CHX₃, three hydrogen atoms replaced
• Tetrahalomethane, CX₄, all four hydrogen atoms replaced

Analogs with carbon atom replaced with a heavier group 14 element are also known:

• Monohalosilane, SiH₃X (with silicon, related to silane)
• Monohalogermane, GeH₃X (with germanium, related to germane)
• Monohalostannane, SnH₃X (with tin, related to stannane)

• Methyl halide transferase, an enzyme producing some methyl halides