The body is searching for a new director-general to replace Brazilian Roberto Azevedo at the end of August.
Boris Johnson said Mr Fox was a "passionate advocate of multilateralism" with "detailed knowledge" of global trading.
Labour said the WTO would "immediately discount" Mr Fox for the role.
Shadow international trade secretary Emily Thornberry said it was "extraordinary" Mr Johnson would choose a candidate he fired from his role after becoming PM, adding: "There will be little trust in somebody who promised so much in regards to Britain's future trade yet delivered so little."
Mr Fox, a Conservative MP since 1992, was an ardent backer of the UK's exit from the EU.
He said he was "honoured" to be nominated, adding: "I believe that if we want to keep the WTO relevant and vibrant our task is clear: Update, strengthen and reform.
"We must ensure that global trade works for everyone."
Seven candidates from other countries have also been nominated for the role.