The Phlegra Montes are a series of sinuous mountain ranges that extends to the north-northeast from the Elysium Rise for nearly , dividing the Martian northern lowlands between the Utopia Planitia to the west and the Amazonis Planitia to the east. The southernmost extent of the Phlegra Montes runs up the Elysium Rise and lies due east of Hecates Tholus, the northernmost of the principal volcanic edifices of the Elysium volcanic province. The mountain massifs display heights of up to , forming one of the most prominent and most extensive mountain ranges on the planet. The ranges' western foothills slope more gradually than those of its more sharply-scarped eastern slope. The massifs begin north of Lockyer Crater and near Adams Crater. One portion of the mountain system is isolated in the area north of Adams Crater, with Tyndall crater situated near the center of the range. The chain of massifs ends around south-southwest of Stokes. The Phlegra Montes take the name of the Phlegra classical albedo feature, which was identified and named by Greek astronomer Eugène Michel Antoniadi in his 1930 publication La Planéte Mars. The International Astronomical Union approved the specific name Phlegra Montes in 1973.