메르케트 섬(스웨덴어: Market)은 발트 해 올란드 제도에 있는 작은 바위섬으로, 스웨덴과 핀란드 영토로 분할되어 있다. 국경선이 나뉜 섬중에서는 세계에서 가장 작은 섬이다. 1809년, 스웨덴과 러시아 사이의 국경선을 확정짓는 프레드릭스함 조약에 의해 섬 중앙을 분할했고, 당시 러시아에 속했던 핀란드가 독립함으로서 러시아령 땅이 핀란드령으로 바뀌었다. 메르케트 섬은 핀란드에서 봤을 때 국토의 가장 서쪽에 위치한 극서점에 해당한다.

 It sits astride the Finnish-Swedish border and is of importance for its computerized remotely
controlled weather station and because it is a lighthouse.

The lighthouse was erected in 1885 by the Russians, who then ruled Finland. Early records are quite difficult to come by and are written in the Russian language. Wooden barracks were constructed on the reef for the workmen who were to build the light. They began to lay its foundation from the rock quarried on the site. A tremendous storm swept away the barracks and the portion of the foundation that had been completed. Three men were lost to the angry sea. After this disaster, plans were revised and stone for the new foundation was quarried and cut to proper size in the Helsinki area and ferried to Market Reef ready to be set into place. The work crews slept aboard a ship anchored nearby and ferried to and from the construction site daily. Work was completed in a year.

During ensuing years two additional buildings were added and connected to the lighthouse by an elevated catwalk some 15 feet in the air. Access to the catwalk is via a series of iron rungs set in the wall of the furthest building or by a steel ladder at the lighthouse end. The middle building is the power generation site for the complex