Lesley Millman Sibner (August 13, 1934 – September 11, 2013) was an American mathematician and professor of mathematics at Polytechnic Institute of New York University.
She earned her Bachelors at City College CUNY in Mathematics.
She completed her doctorate at Courant Institute NYU in 1964 under the joint supervision of Lipman Bers and Cathleen Morawetz.
Her thesis concerned partial differential equations of mixed-type.