Fishing village and bay on the south-western coast of the Isle of Man, in the parish of Kirk Christ Rushen.

The older Manx name is Purt Chiarn, and a Manx dictionary of the period gives Purt-sheearan, adding that it was then generally called Port Iron. Feltham, writing at the end of the eighteenth century, gave the name as Earn or Iron, from the bay lying opposite Ireland, and described a beautiful natural harbour which a pier built at small expense would render commodious and give twenty-five feet of water.

An account published in 1845 describes the village as consisting of about forty houses and states that its herrings were held superior to all others. Port Erin worked as one of the southern stations of the Manx fleet. Evidence taken at Peel in August 1864 by the Royal Commission on Sea Fisheries returned 120 numbered boats to Castletown including Port St Mary, Derbyhaven and Port Erin, out of about 300 in the Island, and one witness observed that there was generally more fish off Port Erin and that its improvement would be a great advantage.

Improvement was slow and expensive. The Isle of Man Harbours Act 1863 authorised harbour dues to be taken at Port Erin to fund the works, against a loan of £58,200 from the Public Works Loan Commissioners. When the dues proved insufficient, the Act of 1864 charged any deficiency, to a limit of £1,600 a year, on the surplus customs revenue of the Island, and later legislation charged it instead on the £10,000 payable into the Exchequer. Port Erin was the only harbour in the Island still raising revenue by dues.

The bay is a horseshoe, with Bradda Head rising to the north. Above the village are a circle of graves on the hill, and on the Mull between Port Erin and Cregneash the circle known as Rhullick y lagg shliggagh. St Catherine's Well flows near the shore, and a lifeboat station was opened in 1883.