|Millennium:||1st millennium BC|
|161 BC by topic|
|Gregorian calendar||161 BC|
|Ab urbe condita||593|
|Ancient Egypt era||XXXIII dynasty, 163|
|- Pharaoh||Ptolemy VI Philometor, 20|
|Ancient Greek era||154th Olympiad, year 4|
|Balinese saka calendar||N/A|
|Chinese calendar||己卯年 (Earth Rabbit)|
2536 or 2476
— to —
庚辰年 (Metal Dragon)
2537 or 2477
|Coptic calendar||−444 – −443|
|Ethiopian calendar||−168 – −167|
|- Vikram Samvat||−104 – −103|
|- Shaka Samvat||N/A|
|- Kali Yuga||2940–2941|
|Iranian calendar||782 BP – 781 BP|
|Islamic calendar||806 BH – 805 BH|
|Minguo calendar||2072 before ROC|
|Seleucid era||151/152 AG|
|Thai solar calendar||382–383|
−34 or −415 or −1187
— to —
−33 or −414 or −1186
Year 161 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Messalla and Strabo (or, less frequently, year 593 Ab urbe condita) and the Third Year of Houyuan. The denomination 161 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
- The rebel Seleucid general and ruler of Media, Timarchus, who has distinguished himself by defending Media against the emergent Parthians, treats Demetrius I's violent accession to the Seleucid throne as the excuse to declare himself an independent king and extend his realm from Media into Babylonia.
- With the restoration of peace in Judea, an internal struggle breaks out between the supporters of Judas Maccabeus and the Hellenist party. The influence of the Hellenic Party all but collapses in the wake of the Seleucid defeat.
- The Jewish High Priest Menelaus, who is supported by the Hellenist party, is removed from office and is executed. His successor is a moderate member of the Hellenist party, Alcimus. However, when Alcimus executes sixty Jews who are opposed to him, he finds himself in open conflict with the Maccabees. Alcimus flees from Jerusalem and goes to Damascus to ask the Seleucid king, Demetrius I, for help.
- The Maccabees, led by Judas Maccabeus, and a Seleucid army, led by the Seleucid general Nicanor, fight the Battle of Adasa, near Beth-horon. Maccabeus wins the battle and Nicanor is killed.
- Ptolemy VIII Euergetes, now king of Cyrenaica, convinces the Roman Senate to back his claim for control of Cyprus, but the Egyptian king Ptolemy VI Philometor ignores this threat, and after Ptolemy VIII Euergetes' attempt to conquer the island fails, the Roman Senate disengages from the dispute.
- The Roman playwright Terence's plays Eunuchus (The Eunuch) and Phormio are first performed.
- Envoys of Judas Maccabeus conclude a treaty of friendship with the Roman Senate.
- Marcus Pomponius, praetor in 161 BC, obtained a decree of the senate, forbidding philosophers and rhetoricians from living at Rome.
- Cleopatra III, queen of Egypt from 142 BC (d. 101 BC)
- Demetrius II Nicator, king of the Seleucid Empire from 145 BC and 129 BC (d. 125 BC)