In the film Titanic, did the story of Jack and Rose actually happen in real life?
Is Jack and Rose's love story real?
Then the answer will be, No.
But there are other secondary characters who are based on real-life people. History.com tried to list them.
But many people draw a parallel between Jack and Rose to Romeo and Juliet, forbidden love, rich-poor, and R+J. And also from eyeforfilm:
Having made a name for himself as a skilled sci-fi and action director, James’s decision to make a period love story – which he pitched to Fox as “Romeo and Juliet on the Titanic”
No, the love story wasn't real. Some of the events were based on true events (i.e. The Unsinkable Molly Brown demanding the lifeboat go back to look for survivors), but Jack and Rose were pure fiction.
Interestingly, there was a Joseph Dawson aboard the Titanic, and his gravestone (simply marked "J Dawson") has been the focal point of some fans of the movie.