An ink composition is provided that includes (A) an acid-generating compound having an anion represented by any one of Formulae (I) to (XI), (B) a cationically polymerizable compound, and (C) a colorant. ##STR00001## (In the formulae, R.sup.1 to R.sup.3 independently denote a monovalent organic group, Rb.sup.1 to Rb.sup.3, Rf.sup.1, and Rf.sup.2 independently denote a perfluoroalkyl group, a perfluoroaryl group, or an aryl group substituted with at least one fluorine atom or perfluoroalkyl group, X.sup.1 to X.sup.3 independently denote a monovalent organic group, and Y.sup.1 denotes a hydrogen atom or a monovalent organic group.)