Leslie Copus Peltier (January 2, 1900 – May 10, 1980) was an American amateur astronomer. Harlow Shapley once described him as "the world's greatest non-professional astronomer".
Leslie Copus Peltier was born in Delphos, Ohio. Delphos is located in northwestern Ohio in both Van Wert and Allen County. His homeplace was located on South Bredeick Street, and his home is still standing today. The home was known as Brookehaven. Peltier married Dorothy Nihiser in November 1933. An amateur astronomer, he was a prolific discoverer of comets and also a persistent observer of variable stars and member of the AAVSO. He was co-discoverer of 12 comets, 10 of which carry his name, and over a span of more than 60 years made more than 132,000 variable star observations.
He wrote the heart-warming autobiographical Starlight Nights (ISBN 0-933346-94-8), which evokes the magic of stargazing in simpler days, on a farm and without light pollution.
Asteroid 3850 Peltier is named in his honor, as is the Leslie C. Peltier Award of the Astronomical League.