Brock Lovett (BILL PAXTON) and his oceanographic crew have been searching the wreck of the R.M.S. Titanic for a diamond, "The Heart of the Ocean," originally worn by Louis XVI that today would be one of the most valuable jewels in the world. Unable to find it, his crew does find a painting of a nude woman wearing what appears to the necklace he's looking for. Thousands of miles away, Rose (GLORIA STUART), a centenarian survivor of the famous tragedy, sees Lovett on TV and recognizes the sketch. Meeting the explorer miles above where the wreck lies, Rose explains that she's the person in the sketch and then goes to tell her story about the Titanic.
Eighty-five years earlier, as a young woman, Rose DeWitt Bukater (KATE WINSLET) comes from high society and is engaged to marry tycoon Cal Hockley (BILLY ZANE), an elitist who doesn't treat her well. Her mother, Ruth (FRANCES FISHER), urges Rose to put up with his behavior so that they'll remain in the wealthy upper class of life. Rose, however, can't stand it anymore, and once at sea, climbs onto the back railing of the Titanic, preparing to jump. Her luck changes when Jack Dawson (LEONARDO DiCAPRIO), a third class passenger who won his way on board via a card game, stops her from jumping.
Soon, a romance flowers between the two, much to the dismay of Cal and Ruth, although the unsinkable Molly Brown (KATHY BATES) thinks it's a hoot that Jack's stirring things up a bit. Their love is threatened, however, when Cal's thug assistant, Spicer Lovejoy (DAVID WARNER), plots to put an end to it, as well as when the Titanic hits an iceberg and begins to sink. As the ship takes on water and Captain Smith (BERNARD HILL) and managing director Bruce Ismay (JONATHAN HYDE) decide what to do, Jack and Rose try to stay together as long as they can.