Lori Lemaris was a love interest of Superman from the Superman comics. Although a major love in Clark's life, the story of their relationship only consisted of one issue.
Lori is a mermaid hailing from the Atlantean city of Tritonis. She first met Clark Kent in college at Metropolis University, where she posed as a wheelchair-bound student to hide her mermaid nature. The two shared a relationship, and Clark eventually proposed. Lori turned him down and, revealing her true nature (and that she knew his own secret), ended the relationship because they were from different worlds. She became a recurring character after that, though not as a love interest to Clark, joining the Aquaman family of heroes. She eventually married a merman named ronal.
Lori was, initally, killed in the massive crossover event known as the Crisis on Infinite Earths. However, the time-altering nature of this event undid her own death. She has continued to appear now-and-again since then.
The story of Lori's college relationship with Clark, Pre-Crisis (Superman vol 1 #129, 1959) and Post-Crisis (Superman vol 2 #12, 1987), except that, post-crisis, Clark had not already become Superman while in college.