子午线高原（英文：Meridiani Planum）或译子午高原、子午线平原，是在火星南纬2度的一个高原，中心位于0°12′N 357°30′E / 0.2°N 357.5°E / 0.2; 357.5，位于子午线高地（Terra Meridiani）的最西侧部分。这个地区有少见的灰色结晶赤铁矿。在地球上赤铁矿常见于温泉或平静的湖泊；因此许多科学家相信在子午线高原的赤铁矿代表了火星古代曾存在温泉或曾经是液态水存在的环境。赤铁矿是当地厚度200至800公尺厚沉积岩地层的一部份。其他子午线高原上的地表特征包含了玄武岩和撞击坑。

Meridiani Planum is a plain located 2 degrees south of Mars' equator (centered at 0°12′N 357°30′E / 0.2°N 357.5°E / 0.2; 357.5), in the westernmost portion of Terra Meridiani. It hosts a rare occurrence of gray crystalline hematite. On Earth, hematite is often formed in hot springs or in standing pools of water; therefore, many scientists believe that the hematite at Meridiani Planum may be indicative of ancient hot springs or that the environment contained liquid water. The hematite is part of a layered sedimentary rock formation about 200 to 800 meters thick. Other features of Meridiani Planum include volcanic basalt and impact craters.