Ubi sunt (lit. 'where are they') is a rhetorical question taken from the Latin phrase Ubi sunt qui ante nos fuerunt?, meaning 'Where are those who were before us?'. Ubi nunc (lit. 'where now') is a common variant.

Sometimes interpreted to indicate nostalgia, the ubi sunt motif is a meditation on mortality and life's transience.

Ubi sunt is a phrase which was originally derived from a passage in the Book of Baruch (3:16–19) in the Vulgate Latin Bible beginning Ubi sunt principes gentium? 'Where are the princes of the nations?'; it became a commonplace in medieval literature.

Variations of the theme occur in a number of Old English homilies, including one which quotes in Latin the following words, which it attributes to St. Augustine: O homo, dic mihi, ubi sunt reges, ubi sunt principes, ubi imperatores, qui fuerunt ante nos... ('O man, tell me, where are the kings, where are the princes, where the emperors, who had been before us...').

These derive from the words of Baruch 3:16–19 in the Vulgate Bible:

16 ubi sunt principes gentium et qui dominantur super bestias quae sunt super terram
17 qui in avibus caeli inludunt
18 qui argentum thesaurizant et aurum in quo confidebant homines et non est finis adquisitionis eorum qui argentum fabricant et solliciti sunt nec est inventio operum illorum
19 exterminati sunt et ad inferos descenderunt et alii loco eorum exsurrexerunt

16 'Where are the princes of the nations, and those who rule over the beasts on earth;
17 those who mock the birds of the air,
18 and who hoard up silver and gold, in which men trust, and there is no end to their getting; those who scheme to get silver, and are anxious, whose labours are beyond measure?
19 They have vanished and gone below, and others have arisen in their place.'
(tr. Revised Standard Version)

This passage forms part of the mass for Holy Saturday, according to the traditional Roman Missal and Breviary.