In the crystal structure of the title compound, C(20)H(39)N(2) (+)·Br(-)·H(2)O, the 1-hexa-decyl-3-methyl-imidazolium cations are stacked along the b axis, forming channels parallel to [100] which are occupied by the bromide anions and water mol-ecules. The crystal is stabilized by O-H⋯Br, C-H⋯O and C-H⋯Br hydrogen-bonding inter-actions, generating a two-dimensional network.
