R.I.B.A. Royal Institute of British Architects.
R.I.P., requiescat in pace=May he (or she) rest in peace.
R.M. Royal Mail; Royal Marines.
R.M.A. Royal Military Asylum; Royal Marine Artillery.
R.M.L.I. Royal Marine Light Infantry.
R.M.S. Royal Mail Steamer; Royal Microscopical Society.
R.N. Royal Navy.
R.N.R. Royal Naval Reserve.
Rob., Robt. Robert.
Roffen. Of Rochester.