Eleny-Nicoleta Ionel is a Romanian mathematician whose research concerns symplectic geometry, including the study of the Gromov–Witten invariants and Gopakumar–Vafa invariant. Among her most significant results are the construction of relative Gromov-Witten invariants of symplectic manifolds, and the proof of the vanishing in codimension at least g of the tautological ring of the moduli space of genus-g curves. She is a professor of mathematics at Stanford University, where she is chair of the mathematics department.