Euler's elastica is defined by a critical point of the total squared curvature under the fixed length constraint, and its L p -counterpart is called p-elastica. In this paper we completely classify all p-elasticae in the plane and obtain their explicit formulae as well as optimal regularity. To this end we introduce new types of p-elliptic functions which streamline the whole argument and result. As an application we also classify all closed planar p-elasticae. Contents 1. Introduction 1 2. The Euler-Lagrange equations 9 3. p-Elliptic functions 11 4. Classification, representation, and regularity of p-elasticae 25 5. Closed p-elasticae 39 Appendix A. First variation of the p-bending energy 45 References 47