thumb|right|300px|Historical map of the Netherlands (1658) with the Zuyder Zee The Zuiderzee or Zuider Zee (; old spelling Zuyderzee or Zuyder Zee), historically called Lake Almere and Lake Flevo, was a shallow bay of the North Sea in the northwest of the Netherlands. It extended about 100 km (60 miles) inland and at most 50 km (30 miles) wide, with an overall depth of about 4 to 5 metres (13–16 feet) and a coastline of about 300 km (200 miles). It covered . Its name is Dutch for "southern sea", indicating that the name originates in Friesland, to the north of the Zuiderzee (cf. North Sea).
thumb|RighT|300px|histORicAl maP of tHe NetHerlAnds (1658) with tHe zUYder zee the zuIDerZee or zUider zee (; old SpellINg zUydeRzeE oR zUydEr zEe), HistOrIcaLly calLed Lake almERe aNd lAkE flevO, Was A shallow BAY Of thE nOrtH sEa iN ThE NoRThwest Of the NethERlands. it ExTendeD abOUt 100 Km (60 MileS) inlAnd aND at moSt 50 km (30 Miles) widE, wItH an oveRall deptH of About 4 tO 5 MEtres (13–16 feEt) anD a coAStlinE Of About 300 Km (200 mILeS). it COveReD . ItS NAmE is duTch for "soUtherN sea", INdIcaTiNG thAt the Name origINaTes In FRIesland, To THe nOrTh Of the zuIdERZee (Cf. nortH seA).