King Mufasa was one of the secondary protagonists in the Lion King franchise. He was Simba's father, Sarabi's husband, Scar's older brother, Nala's father-in-law, Kiara and Kopa's grandfather, Ahadi's oldest son, and the former King of Pride Rock.
In The Lion King, Mufasa and his mate Sarabi give birth to baby Simba, who grows up to be a spunky cub who can't wait to be king of Pride Rock. So Mufasa teaches his son about being king and shows him the whole kingdom.
Eventually, Mufasa saves Simba and Nala from Shenzi, Banzai and Ed after being alerted by Zazu. Mufasa scolds Simba for almost getting him and Nala killed, but Simba said he was only trying to be brave like him; but Mufasa reveals he's only brave when he has to be.
One day, Mufasa's younger brother Scar plots to kill him and Simba, with help from the hyenas. After giving the signal to Shenzi, Banzai and Ed, they cause a wildebeest stampede, in which Simba is almost killed, but is saved in time by Mufasa, who was alerted by Scar. With Simba watching on a safe hill, Mufasa struggles to climb his way back up. He sees Scar at the top and tells him to save him. But Scar grabs Mufasa with his claws (thus making him roar in pain), and with a wicked smile, Scar whispers, "Long live the king!". Horrified, Mufasa realizes Scar's true feelings toward him and he lets go of his brother, sending him flying into the stampede, thus getting trampled and killed. When Simba goes down to help his dad, he soon realizes he's dead and begins to cry. Scar shows up and tricks Simba into believing he caused his father's death and told him to run away and never return. He then sends Shenzi, Banzai and Ed to kill Simba, to which they fail, unbeknownst to Scar.
Many years pass, and Simba is now an adult and afraid to go back home and confront Scar. But eventually, the ghost of Mufasa appears in the night sky and gives Simba confindence and tells him to remember who he is. At the end, Simba finally does go back to the Pride Lands and defeats Scar, taking his rightful place as the new king of Pride Rock and avenging his dad.
In The Lion King II: Simba's Pride, Mufasa's ghost appears at the end to give Kiara and Kovu his blessing. At the end, Mufasa tells Simba that he's proud of him after Kiara and Kovu get married.
In The Lion King 1½, we see Mufasa's story from Timon and Pumbaa's point of view, and they riff on Mufasa's scenes like how Mike, Joel, and the Bots used to do in Mystery Science Theater 3000.
He also appeared as a guest in House of Mouse.
Mufasa's ghost appears again in Kingdom Hearts II to once again give Simba confidence, and he has a flashback where he remembers what Mufasa told him about the stars when he was a kid.
His character was similar to another character James Earl Jones played in Coming to America.
Mufasa was voiced by James Earl Jones and by Keith David in House of Mouse.