Jack Dawson (Leonardo DiCaprio) is a third class passenger who wins his ticket to Titanic in a lucky round of poker. Rose DeWitt Bukater (Kate Winslet) is a first class passenger, engaged to the possessive and obnoxious Caledon Hockley (Billy Zane). Her mother, Ruth (Frances Fisher), is depending on the Hockley fortune to keep them afloat. Hockley is unkind and abusive towards Rose.
Rose feels trapped, and in a moment of hopelessness, she threatens to throw herself off the Titanic, after her grim realization of her life to come. She explains, "I saw my life as if I had already lived it. An endless parade of parties and polo matches, always the same narrow-minded people..."

Jack observes her as she is distraught and crying, and decides to take matters into his own hands. He has seen this woman before....from afar. She took his breath away, but he could only dream of meeting her, as a penniless artist, and a third class passenger. He finds a way to use his charm and his powers of persuasion to change her mind; he saves her from herself, and from then on, Rose is intrigued and totally charmed by this charismatic free spirit who lives life the way he wants to...

Jack is also charmed by the beautiful Rose, but he can see she is a tortured, unhappy, imprisoned spirit fighting to be freed. They can't stay away from each other, and inevitably, as they spend more time together, and realise how close they have become, the fires of passion are ignited. As Jack sketches Rose, wearing only a mystical diamond that Hockley gave her, he seduces her with his eyes, and she realises the extent of her passion for this man. The diamond was called "The Heart of the Ocean", and had been worn by Louis XIV, but now belonged to Caledon Hockley, specifically to be given to his bride... a bride that has now been totally swept away with her growing and inevitable attraction to this energetic and passionate young artist. Jack is captivated, and as they both realise the true depth of their love, and consumate it, Titanic strikes an iceberg hundreds of miles at sea causing pandemonium aboard. As the seamen desperately fight to save it, five of the ship's chambers begin to fill with water, spelling doom for the Titanic.

The water rushes in, forcing the first class women and children to evacuate the boat first. Second and third class people are held in caged hallways. Rose makes the choice to stay with Jack, and in a moment of decision, she flings herself off the lifeboat and rushes into Jack's waiting arms. "You jump, I jump...remember?" says Rose, after Jack screams, "You're so stupid, Rose!! Why'd you do that, Rose, WHY??" There is no lifeboat available for them as the ship sinks, diffusing its passengers into the icy Atlantic waters. Their trust is only but in God, and each other. The water is freezing cold, and there aren't enough boats..not enough by half. Over a thousand people plunge into the icy water that fateful night.

Jack is able to get Rose safely on what appears to be a floating piece of debris from one of Titanic's elegant staterooms. Death slowly creeps up on all of the people in the water. Rose slips into an icy reverie as she floats safely on the board. Jack clings to her hand and freezes to death in the dark, cold Atlantic. Jack gives his life to spare Rose.

She makes it to "the Statue of Liberty", and as she stands on the dock staring at this monument of freedom, she is asked..."What's your name, Miss?" She replies, "Dawson.....Rose Dawson..."