Flintoff, 31, was forced to miss England's emphatic fourth Test innings and 80-run defeat at Headingley last week, which left the series tied at 1-1, because of an injured right knee.
"The swelling in his knee has significantly eased following the decision by the England management team to rest him from the last test match," a statement on the England and Wales Cricket Board (ECB) website said.
"Subject to further rest and intensive treatment, he will be available for selection for the fifth Ashes Test."
Flintoff, who took seven wickets and scored 171 runs in the opening three matches, will retire from Test cricket following the Oval contest which starts on August 20.
James Anderson, England's joint leading wicket-taker in the series with 12, is also expected to play despite injuring his hamstring in the fourth Test.
"As there is no evidence of a significant tear, it is anticipated that he [Anderson] will also be available for selection for next week's final Test," the ECB statement said.