Mersdon (pop. 700) is a village in Oxfordshire, England, built on an elevation near the Kemrese border. This location accounts for the name's etymology, from Anglo-Saxon mǣres + dūn "border hill". The village's claim to fame is due to its being the hometown of the Earl Edward of Mersdon (de Mersdon), who became king of Xliponia in 1190.
Mersdon Abbey, built in the pre-Norman period and lying partly in ruins, houses a library containing some codices that date from Edward's time. Notable among these is the Historia Eaduueardi Comitis, written by the monk Wilberht (Lucidus Meresdunensis), who returned to the abbey from Bovlai in 1209.
In the immediate neighbourhood of Mersdon stand the Rollright Stones of legend.