Happy Birthday, Princess Diana: 50 Rare Images of an Icon

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Long before she became a fashion icon as the Princess of Wales, a young Diana modeled a casual outfit for this family-album portrait taken in the late 1960s.

To commemorate the 50th anniversary of Diana Spencer's birth, LIFE has assembled a celebratory chronicle of her too short yet vibrant time in the public eye. You can get a copy of LIFE's Diana at 50 here.

• Why Princess Diana Mattered