Graham Dwyer, 41, made a brief court appearance and was ordered held without bail for a week, The Irish Times reported. Detective Sgt. Peter Woods said when Dwyer was formally charged a few hours earlier he told police he was not guilty.
Dwyer was arrested Thursday at his home in Foxrock, an upscale suburb of Dublin. He is married with two children.
Elaine O'Hara, 36, disappeared in August 2012. Her car was discovered during the same month, two days after she was last seen, in Shanganagh Cemetery where her mother is buried.
A woman walking her dog found the body in September, concealed in bushes on Killakee Mountain near Dublin.
A bag containing O'Hara's cellphone, keys and other personal items was found in September in a reservoir near Roundwood, about 30 miles south of Dublin.
Investigators said O'Hara, a childcare assistant who also worked for a news agent, had been using a website to find a romantic partner, the Irish Independent reported. Dwyer was apparently identified through searches of her computer and cellphone activity.
Police searched Dwyer's house and seized computers and two vehicles.
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