Star Wars (at least episodes 4 through 7) and Harry Potter are two of my favorite series of all time. "Star Wars: A New Hope" was released in 1977, and twenty years later, we got Harry Potter and the Philosopher's Stone (Harry Potter and the Sorcerer's Stone for those of us in the U.S.).
I recently started re-watching the Harry Potter movies and noticed several similarities between it and the original Star Wars trilogy. For example, both series feature a trio of heroes. In Star Wars, they're Luke, Leia, and Han. In Harry Potter, we have Harry, Hermione, and Ron. Luke and Harry are the "Chosen Ones." Leia/Hermione and Han/Ron are the sidekicks whose relationship gets off to a rocky start but eventually turn into romance. Then there are the Chosen Ones' mentors, Obi-wan and Dumbledore. Both initially took on students (Anakin and Tom Riddle) who not only turn bad but also acquire second names (Darth Vader and Voldemort). The mentors' later pupils (Luke/Harry) wind up defeating the dark predecessors.
There are other similarities, which led me to think that I couldn't be the first person to notice. Sure enough, I found this post that lays out some more similarities side by side.
The point isn't that I think J.K. Rowling copied Star Wars. I don't think she did. There are only so many unique ideas that certain archetypes are bound to pop up again and again. When I started reading the Percy Jackson series, for example, the similarities to Harry Potter were immediately apparent. (Look, another trio, but this time it's Percy, Annabeth, and Grover!) I like all three series very much because of the way the stories were told, and they tell their stories differently. As a writer, don't be afraid that your story has been told (because chances are, there are elements that have been) or that you've stumbled upon the one unique story that the world has never seen (because you haven't). The key is how you tell your story. It's all in the execution, not the idea.