This page is about the ligature, not the simple combination of the letters O and E. For initialisms and the word Oe, see Oe.

"Œ" (lowercase "œ") is a vowel and a letter used in medieval and early modern Latin, and in modern French. The origin of the letter is a ligature for "OE". The character is also referred to by the name eðel, pronounced edh-@l (IPA: ).

The combination denotes a diphthong, IPA [oe], that had a value similar to English "OI". It was used in borrowings from Greek words having the diphthong "OI" ("ΟΙ"). Both classical and modern practice is to write the letters separately, but the ligature was used in medieval and early modern writings, in part because "Œ" was reduced to a simple long vowel (IPA: [e:]) in late Latin.

In German, "Ö" (O with umlaut) is the equivalent. In Danish, Faroese, and Norwegian the equivalent letter is "Ø". It is not interchangeable with Ö in Swedish, Finnish, Icelandic, Estonian, Hungarian and Turkish, as Ö does not there represent O-Umlaut.

Borrowings into English from Latin words featuring "œ" are often spelled with the letter"e", especially in American English. For example, foederal became federal in English, while foetus became fetus only in American English.

In French, "œ" has a predominantly aesthetic use, most prominent in the words cœur ("heart") and sœur ("sister"). Printed documents should ideally use œ systematically whenever "e" follows "o" to make a compound sound resembling eu; that is, without a diaresis (written or at least heard); thus, coefficient does not take a œ, because the o and e sounds are pronounced distinctly. However, many documents are prepared with word processors incapable of inputting or printing this character. Writing generally does not make the distinction between "oe" and "œ".

The symbol "œ" is also used in the International Phonetic Alphabet for the open-mid front rounded vowel. The small capital variant ɶ corresponds to a different sound, the open front rounded vowel.

For computers, when using the Unicode character set, the codes for "Œ" and "œ" are respectively 338 and 339, or 152 and 153 in hexadecimal. In HTML, the HTML character entity references Œand œ can also be used.