The Pied Piper of Hamelin is a folk tale, among others written down by the Brothers Grimm. It tells about a disaster in the town of Hamelin, Germany, that supposedly occurred on June 26, 1284. In that year a man came to Hamelin claiming to be a rat-catcher. The people of Hamelin promised him payment for killing the rats. So the man took a pipe, attracted the rats by his music and made them follow him to the Weser river, where they all drowned. Despite this success the people reneged on their promise and did not pay the rat-catcher.

He left the town, but returned several weeks later. While the inhabitants were in the church, he played his pipe again, this time attracting the children of Hamelin. One hundred thirty boys and girls followed him out of the town, where they were lured into a cave and sealed inside. Depending on the version, at most two children survived.

The earliest mention of the story seems to have been on a glass window placed in the church of Hamelin ca. 1300. It was described in several accounts between the 14th century and the 17th century but it seems to have been destroyed. Based on the surviving descriptions, a modern reconstruction of the window has been created by Hans Dobbertin. It features the colorful figure of the Pied Piper and several figures of children dressed in white.

This window is generally considered to have been created in memory of a tragic historical event for the city. But although there has been a lot of research, no clear explanation can be given of what historical event is behind the reports, see an external link with a list of theories (http://www.hameln.com/tourism/piedpiper/rf_sage_gb.htm). However, the rats were first added to the story in the late 16th century; they miss in all previous accounts.

Theories that have gained some support can be grouped into the following four categories:

• The children fell victim to an accident, either drowning in the river Weser or being buried in a landslide.
• The children contracted some disease during an epidemic and were led out of town to die in order to protect the rest of the city's population from contracting it. An early form of Black Death has been suggested. Others attribute the dancing of the children to be an early reference to Huntington's disease, an inherited disorder. These theories perceive the Piper as a symbolic figure of Death.
• The children left the city to be part of a pilgrimage, a military campaign, or even a new Children's crusade but never returned to their parents. These theories see the unnamed Piper as their leader or a recruiting agent.
• The children willingly abandoned their parents and Hamelin in order to become the founders of their own villages during the colonization of Eastern Europe. Several European villages and cities founded around this time have been suggested as the result of their efforts as settlers. Again the Piper is seen as their leader.

Another possibility (which, it must be emphasised, is only an unsupported guess by the writer of this paragraph) is that the incident is a reminiscence of one of the outbreaks of chorea, or communal dancing mania, which are recorded in a number of European towns during the period of general distress which followed the Black Death. The 'Verstegan/Browning' date, 1376, would be consistent with this.

However, the tradition that the children emigrated in 1284 is so old and well-reported that this date should not be changed. Modern scholars regard the fourth above-mentioned theory as most probable, i. e. that the Pied Piper of Hamelin was a recruiter for the colonization of eastern Europe which took part in the 13th century and that he lead away a big part of the young generation of Hamelin to a region in Eastern Germany.

Decan Lude of Hamelin was reported ca. 1384 to have in his possession a chorus book containing a Latin verse giving an eyewitness account of the event. The verse was reportedly written by his grandmother. This chorus book is believed to have been lost since the late 17th century.

A German version of the phrase seems to have survived in a 1602/1603 inscription found in Hamelin:

Anno 1284 am dage Johannis et Pauli
war der 26. junii
Dorch einen piper mit allerlei farve bekledet
gewesen CXXX kinder verledet binnen Hamelen gebo[re]n
to calvarie bi den koppen verloren

It has been roughly translated into English as:

In the year of 1284, on John's and Paul's day
was the 26th of June
By a piper, dressed in all kinds of colors,
130 children born in Hamelin were seduced
and lost at the place of execution near the Koppen.

Koppen (German: hills) seems to be a reference to one of several hills surrounding the city. Which of them was intended by the verse's author remains uncertain.

The oldest remaining written source is from ca. 1440.

Reportedly, there is a long-established law forbidding singing and music in one particular street of Hamelin, out of respect for the victims.

In 1556 "De miraculis sui temporis" (Latin: Concerning the Wonders of his Times) by Jobus Fincelius mentions the legend. The author identifies the Piper with the Devil

The earliest English account is that of Richard Rowland Verstegan, an antiquary and religious controversialist of partly Dutch descent, in his 'Restitution of Decayed Intelligence' (Antwerp, 1605); unfortunately he does not give his source. He includes the reference to the rats and the idea that the lost children turned up in Transylvania. The phrase 'Pied Piper' seems to have been coined by Verstegan. Curiously enough his date is entirely different from that given above: 22 July 1376. Verstegan's account was copied in Nathaniel Wanley's 'Wonders of the Visible World' (1687), which was the immediate source of Robert Browning's well-known poem (below).

In 1803, Johann Wolfgang von Goethe authored a poem based on the legend. He incorporated references to the story in his version of Faust. The first part of the Drama was first published in 1808 and the second in 1832.

Jakob Grimm and Wilhelm Grimm, siblings known as the Brothers Grimm, drawing from eleven sources included the tale in their collection "Deutsche Sagen" (German Legends), first published in 1816. According to their account two children were left behind as one was blind and the other lame, so neither could follow the others. The rest became the founders of Siebenburgen, Transylvania.

Based probably on the Grimm Brother's version of the tale, Robert Browning wrote a poem of that name which was published in 1849. It places the events on July 22, 1376.

The Pied Piper story is heavily referenced by the Russian poet Marina Tsvetaeva in her poem The Ratcatcher, first published in 1925.