18th King of Rohan, lived 2991TA - 63FA; son of Theodwyn and Eomund; a nephew of Theoden, King of Rohan; Third Marshal of Riddermark.
We meet Eomer in the 2nd part of "The Lord of the Rings", when he along with other riders was pursuing Saruman's orcs. He overtook them and killed every single orc. Then Eomer met Aragorn, Legolas and Gimli, but he didn't give them a warm welcome. He was suspicious of the elf and the dwarf and treated them badly. It seemed as if he was going to start a fight. But all is well that ends well. Thanks to Aragorn, who managed to solve that conflict, everything turned out to be fine.
The Rohirrim are well described in the book: "Their horses were of great stature, strong and clean-limbed; their grey coats glistened, their long tails flowed in the wind, their manes were braided on their proud necks. The Men that rode them matched them well: tall and long-limbed; their hair, flaxen-pale, flowed under their light helms, and streamed in long braids behind them; their faces were stern and keen. In their hands were tall spears of ash, painted shields were slung at their backs, long swords were at their belts, their burnished skirts of mail hung down upon their knees." Eomer was the tallest of them all, and bore a helmet, which was decorated with a horse's tail.
With great interest Eomer listened to Aragorn's tale of the fate of the Fellowship, he gave valuable advice and offered his horses. Eomer was more than sure that the return of Elendil's descendant would definitely lift up the fighting spirit of the Rohirrim. Eomer was truly amazed by the story about the hobbits and a newly forged sword, which as if came out of the legends. However, a law bound Eomer - no one could pass the lands of Rohan without the King's permission. But he broke it - despite him risking everything by helping the Fellowship.
Eomer fought in a lot of difficult battles under the standard, bearing the running horse, white upon green - the emblem of the House of Eorl. He was a fine military leader as well as a brave warrior. Eomer's sword - Guthwine ("friend in battle") - fiercely slashed the orcs, besieging Helm's Deep. Together with Aragorn and the Rohirrim they made a successful sally, and the orcs retreated seeing their swords.
After the Hornburg, Eomer accompanied by Theoden and Gandalf went to Isengard. He was shocked at seeing the destructions, caused by Saruman. Eomer finally convinced the King in Saruman's false nature: "Have we ridden forth to victory, only to stand at last amazed by an old liar with honey on his forked tongue?"
In the 3rd part of the trilogy both Eomer and Theoden were struggling forward to aid Gondor and its people. At the military council it was decided to ask for help. At the fateful hour of the battle of the Pelennor Eomer was in charge of his first uored. At the end of the battle when Theoden was dying he named Eomer his successor.
After the fall of Sauron, Eomer married Lothuriel, daughter of Imrahil Dol Amroth. Eomer died at the age of 93, in FA 63. He was succeeded by his son Elfwine, who continued his father's good reign and was soon called the Fair.