Black Monday refers to specific Mondays when undesirable or turbulent events have occurred. It has been used to designate massacres, military battles and stock market crashes.
- 1209, Dublin – when a group of 500 recently arrived settlers from Bristol were massacred by warriors of the Gaelic O'Byrne clan. The group had left the safety of the walled city of Dublin to celebrate Easter Monday near a wood at Ranelagh, when they were attacked without warning. Although now a relatively obscure event in history, it was commemorated by a mustering of the Mayor, Sheriffs and soldiers on the day as a challenge to the native tribes for centuries afterwards.
- 13 April 1360 – Black Monday (1360), when inclement weather killed men and horses in the army of Edward III during the Hundred Years' War.
- 24 February 1689 – During the Williamite War in Ireland the Protestant inhabitants of Bandon rose up against the Irish Army garrison of the town in an incident known as Black Monday. Bandon was quickly recaptured by Justin MacCarthy.
- 28 October 1929 – Stock markets in the United States began to crash, prior to Black Tuesday.
- 17 May 1954, Washington, D.C. – Following the Supreme Court's decision in Brown v. Board of Education, U.S. Representative John Bell Williams (D-Mississippi) coined the term “Black Monday” on the floor of Congress to denote Monday, 17 May 1954, the date of the Supreme Court's decision. In opposition to the decision, white citizens' councils formally organized throughout the south to preserve segregation and defend segregated schools.
- 19 September 1977, Youngstown, Ohio, U.S. – Youngstown Sheet and Tube closes its doors and furloughs 5000 workers, devastating the Youngstown economy: See Economy of Youngstown, Ohio § Black Monday
- 19 October 1987 – Black Monday (1987) Stock markets around the world crashed, shedding a huge value in a very short time.
- 8 October 1990 – 1990 Temple Mount riots in Jerusalem
- 29 September 2008 – September 2008 stock market crash. Following the bursting of the US Housing Bubble, stock markets around the world crashed, leading to the Great Recession.
- 20 July 2009, Berlin – Only 330 of the 1,260 of the Berlin S-Bahn's train cars were good for operation. Earlier in the month 380 (30.2%) train cars were removed, making the total removed on 20 July was at 550 (43.7%).
- 30–31 July 2012 – 2012 India blackouts: Due to an increase in power usage brought on by extreme heat in the summer of 2012, circuit breakers along the 400 kV Bina-Gwalior line tripped and caused critical outages that affected nearly half of India (22 out of 28 states), or 620 million people (nearly 9% of the world's population).
- 24 August 2015 – 2015 Chinese stock market crash. The SSE Composite Index declined by 8.45%.
- 3 October 2016 – Strikes and demonstrations by women in Poland protesting against proposed legislation for a total ban on abortion.
- The day following the final Sunday of the National Football League regular season (Week 17) on which numerous coaches and general managers of underperforming teams are fired or resign their positions. First use of the phrase was attributed by a pair of writers in the New York Times to a 1998 Associated Press story, "Black Monday for NFL Coaches". The term is also sometimes used in reference to the day following the annual NFL Draft where players' contracts may be terminated once new players are added to a roster.
- An old schoolboys' name for the first Monday after the holidays.