"The Girl I Left Behind", also known as "The Girl I Left Behind Me", is an English folk song dating back to the Elizabethan era. It is said to have been played when soldiers left for war or a naval vessel set sail. According to other sources the song originated in 1758 when English Admirals Hawke and Rodney were observing the French fleet. The first printed text of the song appeared in Dublin in 1791. A popular tune with several variations, "The Girl I Left Behind Me", may have been imported into America around 1650 as "Brighton Camp", of which a copy dating from around 1796 resides in the Bodleian Library, Oxford.

The melody is derived from a traditional Irish melody known as An Spailpín Fánach, meaning "The Wandering Labourer", which was collected by Edward Bunting in The Ancient Music of Ireland (1840). An Spailpín Fánach continues to exist as a popular sean-nós song in traditional Irish-speaking communities, although it is unknown whether its lyrics predate "The Girl I Left Behind Me" or if the lyrics were a later addition to the An Spailpín Fánach melody.

The first known printed text of a song with this name appeared in the serial song collection The Charms of Melody, Dublin, Ireland, issue no. 72, printed in Dublin from 1791 and in Exshaw's Magazine (Dublin, September 1794). The earliest known version of the melody was printed about 1810 in Hime's Pocket Book for the German Flute or Violin (Dublin), vol. 3, p. 67, under the title "The Girl I left Behind Me" (National Library of Ireland, Dublin). Theodore Ralph claimed that it was known in America as early as 1650, under the name "Brighton Camp", but there is no evidence to support this assumption, and the only known tune of "Brighton Camp" differed from that of the song in question.

It has many variations and verses, for example "Blyth Camps, Or, the Girl I left behind Me" (1812, Newcastle), "Brighton Camp, or the Girl I left behind Me" (1815, Dublin, from which the "Brighton" title probably came), "Nonesuch," and others. Here is one example:

All the dames of France are fond and free
And Flemish lips are really willing
Very soft the maids of Italy
And Spanish eyes are so thrilling

Still, although I bask beneath their smile,
Their charms will fail to bind me
And my heart falls back to Erin's isle
To the girl I left behind me.

A number of Irish-language and English-language songs were set to this tune in Ireland in the 19th century, such as "An Spailpín Fánach" (translated into English as "The Rambling Labourer"), "The Rare Old Mountain Dew" (published New York, 1882) and in the 20th century, such as "Waxie's Dargle".

In England the tune is often known as "Brighton Camp" and is used for Morris dancing.

The hours sad I left a maid
A lingering farewell taking
Whose sighs and tears my steps delayed
I thought her heart was breaking
In hurried words her name I blest
I breathed the vows that bind me
And to my heart in anguish pressed
The girl I left behind me

Then to the east we bore away
To win a name in story
And there where dawns the sun of day
There dawned our sun of glory
The place in my sight
When in the host assigned me
I shared the glory of that fight
Sweet girl I left behind me

Though many a name our banner bore
Of former deeds of daring
But they were of the day of yore
In which we had no sharing
But now our laurels freshly won
With the old one shall entwine me
Singing worthy of our size each son
Sweet girl I left behind me

The hope of final victory
Within my bosom burning
Is mingling with sweet thoughts of thee
And of my fond returning
But should I n'eer return again
Still with thy love i'll bind me
Dishonors breath shall never stain
The name I leave behind me