Ó, ó (o-acute) is a letter in the Czech, Dobrujan Tatar, Emilian-Romagnol, Faroese, Hungarian, Icelandic, Kashubian, Polish, Slovak, Karakalpak, and Sorbian languages. The symbol also appears in the Afrikaans, Catalan, Dutch, Irish, Nynorsk, Bokmål, Occitan, Portuguese, Spanish, Italian and Galician languages as a variant of the letter "o". It usually represents a vowel sound longer than or slightly different from that represented by plain "o", although in some cases its sound is notably different (as in modern Polish, where it is pronounced the same as "u"). In some cases it represents the vowel "o" with a particular tone (for example, a high rising tone in Vietnamese). It is sometimes also used in English for loanwords.

In Chinese pinyin ó is the yángpíng tone (阳平, high-rising tone) of "o".

Ó is the 24th letter of the Czech alphabet and the 28th letter of the Slovak alphabet. It represents /oː/.

Ó is the 21st letter of Dobrujan Tatar alphabet, represents the mid rounded half-advanced ATR or soft vowel /ɵ/ as in "tór" [t̶ɵr̶] 'background'

In Dutch, the acute Ó accent is used to mark different meanings for words, for example voor and vóór ("for" / "before"), or vóórkomen and voorkómen ("to occur" / "to prevent").

In Emilian, ó is used to represent [o], e.g. sótt [sotː] "dry".

Ó is the 18th letter of the Faroese alphabet and represents /œ/ or /ɔuː/.

Ó is the 25th letter of the Hungarian alphabet. It represents the long vowel /oː/.