Lönkytin is a high, rocky islet. It is located about 10 kilometres (6.2 mi) west-northwest of the mouth of the Kiiminkijoki river, to the east of the Oulu and Kemi deep-water route. The island has a radar reflector. It is near one of the deepest parts of the Finnish sector of the Gulf of Bothnia, at some places reaching a depth of 50 metres (160 ft). The second-closest island to the east is Satakarinletto.