Daddy Long Legs (movie, 1955)

Wealthy American, Jervis Pendleton has a chance encounter at a French orphanage with a cheerful 18-year-old residen, and anonymously pays for her education at a New England college. She writes letters to her mysterious benefactor regularly, but he never writes back. Several years later, he visits her at school, while still concealing his identity, and—despite their large age difference—they soon fall in love.