A macer is an officer who bears a ceremonial mace.

Macer is a Roman cognomen meaning "lean".

• Aemilius Macer was a Roman poet of the late Republic.
• Aemilius Macer (jurist) a Roman jurist of the third century AD.
• Quintus Baebius Macer, Roman senator of first and second centuries AD.
• Gaius Caesonius Macer Rufinianus, Roman military officer of the second century AD.
• Lucius Caesonius Lucillus Macer Rufinianus, Roman senator and military officer of the third century AD.
• Publius Calpurnius Macer Caulius Rufus, Roman senator of the second century AD.
• Lucius Clodius Macer was a legatus of the Roman Empire in Africa in the time of Nero.
• Gaius Licinius Macer (d. 66 BC), was an official and annalist of ancient Rome.
• Licinius Macer Calvus, Roman orator and poet of the first century BC.
• Martius Macer, Roman general who commanded a force of gladiators under Otho.

Also, Macer may refer to:

• Karlee Macer, Democratic member of the Indiana House of Representatives.
• Monica Macer, American writer and producer.
• Reinald Macer (died 1213), Cistercian monk and bishop.
• Joe Macer, fictional character from the BBC soap opera EastEnders.
• Nick Macer, British nurseryman.
• Kate Macer, a character in the 2015 film Sicario, played by Emily Blunt
• Megan and Liz fans are called Macers