Morwen of Lossarnach was the wife of Thengel, 16th King of Rohan. They married in year 2943 of the 3rd age and had five children; one son, Théoden and four daughters, the youngest of whom was Théodwyn, mother of Éowyn and Éomer. Morwen and Thengel initially lived in Lossarnach in Gondor.

On the death of Thengel’s father King Fengel (from whom Thengel was estranged) they returned to Rohan. Morwen was known to the people of Rohan as Steelsheen.