Former WA Liberal leader Mike Nahan has announced he will retire from politics at the next election.

The Riverton MP said in a statement to party members he would not nominate for the seat, which he won at the 2017 election with a margin on 4.4 per cent.

Former WA Liberal leader Mike Nahan. Credit:AAP Image/Rebecca Le May

"I have decided not to nominate and re-contest the 2021 State Election," Dr Nahan said.

"I am very grateful to the many people who have urged me to re-contest. I have considered their views and representations very carefully and respectfully, indeed up to this very last minute. It is with a heavy heart that I disappoint them.