Mer or MER may refer to:

• Francis Mer (born 1939), French businessman, industrialist and politician, former Minister of the Economy
• Gideon Mer (1894-1961), Israeli scientist working mostly on the eradication of malaria
• Mer people, a people of the Kathiawar region in Saurashtra, India
• M.E.R. (Maria Elizabeth Rothmann), Afrikaner writer

-mer and mer- (from Greek meros, part) are affixes used in the following words.

The terms zonal and meridional are used to describe directions on a globe. Zonal means "along a latitude circle" or "in the west–east direction"; while meridional means "along a meridian" or "in the north–south direction".