Erottaja (Swedish: Skillnaden), meaning "the separator", is a public square near the centre of Helsinki, Finland.
Erottaja square has been selected as the official geographic "zero point" of Helsinki. Distances to all other cities in Finland are measured starting from here. In practice, the square functions as the meeting point of central Helsinki's two famous streets, Esplanadi and Mannerheimintie. The square is the western endpoint of Esplanadi, with the eastern endpoint being at the market square. Mannerheimintie, the second longest (longest being Hämeentie) and most famous street in Helsinki, begins at Erottaja and continues northwest, past the districts of Töölö and Ruskeasuo, until finally merging with a highway leading outside the city.
There is also a minor bus station at Erottaja. Very few lines start or end there, most of them start or end at the Kamppi Center or at Rautatientori.
Erottaja is also famous for being the most expensive lot in the original Finnish edition of Monopoly, even more expensive than Mannerheimintie (the second most expensive lot). This has earned the square fame even outside Helsinki.