The announcement follows the election in December of Nicholas Grimshaw as RA president. He replaced Professor Phillip King, who stepped down after five years in office because of health problems.
Ritchie and Cook have pledged to play an active role in the RA's schools as well as its forum and architectural programme. Their appointment was confirmed at the RA's general assembly, also last December.
The former professor of architecture, Trevor Dannatt, who was appointed in 1988, has been named Professor Emeritus.
Commenting on the new line-up, Grimshaw said: 'We are delighted with these new appointments. Over the next three to four years we look forward to the joint professors putting the RA at the forefront of international architectural debate and development, while promoting the activities of British architects and highlighting the creative use of new technology.'
Historically, one person has held the professorship but, following an RA review, it was decided to split responsibilities between two architects.
Established in 1768, the position has been held by a litany of distinguished architects including John Soane, C R Cockerell and Maxwell Fry.
by Clive Walker