Elliptic curves form a family of Diophantine equations. They have manyfascinating properties, some of which we shall touch upon in this chapter.Elliptic curves have provided the testing ground for numerous theoremsand conjectures in number theory, and there are many number theoreticproblems, such as the congruent number problem, whose solution leadsnaturally to one or more elliptic curves. Most notable among the recentapplications of elliptic curves is Wiles' proof of Fermat's Last Theorem.