Boromir, a fictional character from J. R. R. Tolkien's fantasy universe of Middle-earth, is the eldest son of Denethor, last Steward of Gondor in the Third Age of Middle-earth. He was one of the Nine Walkers who made up the Fellowship of the Ring in The Lord of the Rings.
Warning: Wikipedia contains spoilers
Seduced by the lure of the ring, he tries to seize it from Frodo, leading to the breaking of the Fellowship. He dies trying to prevent Orcs from capturing Merry and Pippin in the beginning of The Two Towers, thereby redeeming himself for trying to take the ring.
In the movie The Lord of the Rings: The Fellowship of the Ring, Boromir is played by Sean Bean. Differing from the book, Boromir dies at the end of the film instead of the beginning of The Two Towers.
The extended cut (not the original theatrical version) of the movie of The Two Towers includes a scene not taken from the book in which Boromir and his brother Faramir see each other for the last time, and we see their father Denethor's attitude toward his two sons.