It's possible you're thinking of:
* The Lady of the Lake (1915): This silent film starred Loretta Young as the titular character.
* The Lady of the Lake (1988): This was a TV movie directed by Gary Nelson and starring Anne Archer as the Lady of the Lake.
* The Lady of the Lake (1954): This movie musical adaptation of the Arthurian legend featured Alan Young, Katherine Dunham, and Bartholomew Platt in the lead roles.
Please clarify which "The Lady of the Lake" you are interested in, and I can provide you with the cast list.