October is the tenth month of the year in the Julian and Gregorian calendars. Its length is 31 days. The eighth month in the old calendar of Romulus c. 750 BC, October retained its name (from Latin and Greek ôctō meaning "eight") after January and February were inserted into the calendar that had originally been created by the Romans. In Ancient Rome, one of three Mundus patet would take place on October 5, Meditrinalia October 11, Augustalia on October 12, October Horse on October 15, and Armilustrium on October 19. These dates do not correspond to the modern Gregorian calendar. Among the Anglo-Saxons, it was known as Winterfylleth (Ƿinterfylleþ), because at this full moon, winter was supposed to begin.
October is commonly associated with the season of spring in parts of the Southern Hemisphere, and autumn in parts of the Northern Hemisphere, where it is the seasonal equivalent to April in the Southern Hemisphere and vice versa.
This list does not necessarily imply either official status or general observance.
Non-Gregorian: 2023 dates
(All Baha'i, Islamic, and Jewish observances begin at the sundown prior to the date listed, and end at sundown of the date in question unless otherwise noted.)
- List of observances set by the Bahá'í calendar
- List of observances set by the Chinese calendar
- List of observances set by the Hebrew calendar
- List of observances set by the Islamic calendar
- List of observances set by the Solar Hijri calendar
- Black History Month in the United Kingdom
- In Catholic Church tradition, October is the Month of the Holy Rosary.
- Breast Cancer Awareness Month
- Health Literacy Month
- International Walk to School Month
- Medical Ultrasound Awareness Month
- Rett Syndrome Awareness Month
- World Blindness Awareness Month
- World Menopause Month
- Vegetarian Awareness Month
The last two to three weeks in October (and, occasionally, the first week of November) are normally the only time of the year during which all of the "Big Four" major professional sports leagues in the U.S. and Canada schedule games; the National Basketball Association begins its preseason and about two weeks later starts the regular season, the National Hockey League is about one month into its regular season, the National Football League is about halfway through its regular season, and Major League Baseball is in its postseason with the League Championship Series and World Series. To date there have been 30 occasions in which all four leagues played games on the same day (an occurrence popularly termed a sports equinox), with the most recent of these having taken place on October 30, 2023. Additionally, the Canadian Football League is typically nearing the end of its regular season during this period, while Major League Soccer is beginning the MLS Cup Playoffs.
- American Archives Month
- National Adopt a Shelter Dog Month 
- National Arts & Humanities Month
- National Bullying Prevention Month
- National Cyber Security Awareness Month
- National Domestic Violence Awareness Month
- Filipino American History Month
- Italian-American Heritage and Culture Month
- Polish American Heritage Month
- National Work and Family Month
- American Pharmacist Month
- Celebrating All of October Dwarfism/Little People/Short Stature/Skeletal Dysplasia Awareness
- Dwarfism/Little People Awareness Month 
- Eczema Awareness Month 
- National Dental Hygiene Month
- National Healthy Lung Month
- National Infertility Awareness Month
- Liver Awareness Month
- National Lupus Erythematosus Awareness Month
- National Physical Therapy Month
- National Spina Bifida Awareness Month
- Sudden Infant Death Syndrome Awareness Month  (United States)
United States, culinary
- National Pizza Month
- National Popcorn Poppin' Month
- National Pork Month
- National Seafood Month
Movable, 2022 dates
- Oktoberfest celebrations (varies globally based on area)
- Astronomy Day: October 1
- World Cerebral Palsy Day: October 6
- World College Radio Day: October 7
- Earth Science Week: October 9–15
- See also Movable Western Christian observances
- See also Movable Eastern Christian observances
First Sunday: October 2
- Daylight saving time begins (Australia)
- Father's Day (Luxembourg)
- Grandparents Day (Queensland, Australia, United Kingdom)
- Teachers' Day (Belarus, Latvia, Ukraine)
First full week: October 2–8
- Albuquerque International Balloon Fiesta (United States)
- Mental Illness Awareness Week (United States)
First Monday: October 3
- Child Health Day (United States)
- Children's Day (Chile, Singapore)
- Labour Day (Australian Capital Territory, New South Wales, South Australia, Queensland, Australia)
- Peat Cutting Monday (Falkland Islands)
- Thanksgiving (Saint Lucia)
- World Architecture Day
- World Habitat Day
First Tuesday: October 4
First Wednesday: October 5
First Thursday: October 6
- National Poetry Day (UK, Ireland)
First Friday: October 7
Second Saturday: October 8
- International Migratory Bird Day (Mexico, Central and South America, and the Caribbean)
- Home Movie Day (International observance)
- National Tree Planting Day (Mongolia)
Second Sunday: October 9
Week of October 9: October 9–15
- Fire Prevention Week (Canada, United States)
Week of October 10: October 9–15
Second Monday: October 10
- Columbus Day (United States)
- Fraternal Day (Alabama, United States)
- Health and Sports Day (Japan)
- Mother's Day (Malawi)
- Norfolk Island Agricultural Show Day (Norfolk Island)
- Thanksgiving (Canada)
- National Day (Republic of China)
Second Tuesday: October 11
Second Wednesday: October 12
Wednesday of second full week in October: October 12
Second Thursday: October 13
Second Friday: October 14
Third Saturday: October 15
Third Sunday: October 16
Third Monday: October 17
- Heroes' Day (Jamaica)
- Mother's Day (Argentina)
- Nanomonestotse (Native American communities)
- Boss's Day (United States, Canada, Lithuania and Romania)
Third Thursday: October 20
Fourth Saturday: October 22
Week of Fourth Wednesday: October 23–29
Fourth Monday: October 24
Fourth Wednesday: October 26
Last Friday: October 28
- National Bandanna Day (Australia)
- Nevada Day (Nevada, United States) (though the state was actually admitted on October 31, 1864)
- Teacher's Day (Australia) (If the last Friday is on October 31, this holiday is moved to November 7)
Last Sunday: October 30
- European Summer Time ends
- Grandparents Day (New South Wales, Australia)
- Székely Autonomy Day (Romania)
Last Monday: October 31
- October 1
- Armed Forces Day (South Korea)
- Children's Day (El Salvador, Guatemala, Sri Lanka)
- Day of Prosecutors (Azerbaijan)
- Continuance of German-American Heritage Months, which runs from September 15 – October 15  (United States)
- Continuance of National Hispanic Heritage Month which runs from September 15 – October 15 (United States),
- Ground Forces Day (Russia)
- Independence Day (Cyprus)
- Independence Day (Nigeria)
- Independence Day (Palau)
- Independence Day (Tuvalu)
- International Coffee Day
- International Day of Older Persons
- International Music Day
- Lincolnshire Day (United Kingdom)
- National Day of the People's Republic of China (People's Republic of China)
- Pancasila Sanctity Day (Indonesia)
- Teacher's Day (Uzbekistan)
- Unification Day (Cameroon)
- World Vegetarian Day
- October 2
- October 3
- October 4
- October 5
- October 6
- Day of Commemoration and National Mourning (Turkmenistan)
- Dukla Pass Victims Day (Slovakia)
- German-American Day (United States)
- Memorial Day for the Martyrs of Arad (Hungary)
- National Noodle Day (United States)
- Teachers' Day (Sri Lanka)
- Yom Kippur War commemorations:
- October 7
- October 8
- October 9
- October 10
- October 11
- October 12
- Children's Day (Brazil)
- Discovery of America by Columbus-related observances (see also October 8):
- Columbus Day (United States, Honduras)
- Día de la Hispanidad or Fiesta Nacional de España, also Armed Forces Day (Spain)
- Día de la Raza (El Salvador, Uruguay)
- Día de la Resistencia Indígena, "Day of Indigenous Resistance" (Venezuela)
- Día de las Américas (Belize)
- Día de las Culturas, "Day of the Cultures" (Costa Rica)
- Día del Respeto a la Diversidad Cultural, "Day of respect for cultural diversity" (Argentina)
- Discovery Day (The Bahamas, Colombia)
- Feast for Life of Aleister Crowley, celebrated as "Crowleymas" (Thelema)
- Fiesta Nacional de España (Spain)
- Freethought Day
- Independence Day (Equatorial Guinea), celebrates the independence of Equatorial Guinea from Spain in 1968.
- UN Spanish Language Day (United Nations)
- October 13
- October 14
- October 15
- Breast Health Day (Europe)
- Evacuation Day (Tunisia)
- Global Handwashing Day
- King Father's Commemoration Day (Cambodia)
- National Latino AIDS Awareness Day (United States)
- Pregnancy and Infant Loss Remembrance Day (United States and Canada)
- Spirit Day (International observance)
- Teachers' Day (Brazil)
- White Cane Safety Day (United States)
- October 16
- October 17
- October 18
- October 19
- October 20
- October 21
- Apple Day (United Kingdom)
- Armed Forces Day (Honduras)
- Egyptian Naval Day (Egypt)
- Indian Police Commemoration Day (India)
- International Day of the Nacho
- National Nurses' Day (Thailand)
- Ndadaye Day (Burundi)
- Overseas Chinese Day (Taiwan)
- Trafalgar Day (the British Empire in the 19th and early 20th century)
- October 22
- October 23
- October 24
- October 25
- October 26
- October 27
- October 28
- October 29
- October 30
- Anniversary of the Declaration of the Slovak Nation (Slovakia)
- Day of Remembrance of the Victims of Political Repressions (former Soviet republics, except Ukraine)
- Indonesian Banknote Day (Indonesia)
- International Orthopaedic Nurses Day
- Mischief Night (United States and Canada)
- Thevar Jayanthi (Thevar community, India)
- October 31
- Start of Allhallowtide October 31 – November 6
- The first day of the Day of the Dead, celebrated until November 2 (Mexico)
- Día de la Canción Criolla (Peru)
- Eve of Winter, the eve of the first day of winter in the Northern hemisphere:
- Girl Scouts Founders Day (United States)
- King Father's Birthday (Cambodia)
- National Unity Day (India)
- Reformation Day (Slovenia, parts of Germany, Chile, El Salvador, Dominican Republic, Evangelical Churches and Lutheran Churches)
- Saci day (Brazil)
- World Savings Day
- Statehood Day Nevada, United States
- Eric Whitacre composed a piece based on this month, titled October.
- Neil Gaiman wrote a story personifying the month, titled "October in the Chair", for his 2006 collection Fragile Things.
- Ray Bradbury published a collection of short stories titled The October Country in 1955.
- The song October doth before us go celebrates the progression of spring (from the perspective of the Southern Hemisphere).
- Chisholm, Hugh, ed. (1911). . Encyclopædia Britannica (11th ed.). Cambridge University Press.
- "Gemstone Leaflet" (PDF). Jewelers of America. Archived from the original (PDF) on 2012-02-22. Retrieved Jan 22, 2012.
- SHG Resources. "Birth Months, Flowers, and Gemstones". SHG Resources. Archived from the original on 2012-09-11. Retrieved 2011-11-01.
- The Earth passes the junction of the signs at 22:59 UT/GMT October 22, 2020, and will pass it again at 04:51 UT/GMT October 23, 2021.
- "Astrology Calendar", yourzodiacsign. Signs in UT/GMT for 1950–2030.
- "CATHOLIC ENCYCLOPEDIA: Special Devotions For Months". Newadvent.org. Retrieved 2012-10-24.
- "Health Literacy Month – Finding the Right Words for Better Health". www.healthliteracymonth.org.
- "SDMS Medical Ultrasound Awareness Month". www.sdms.org.
- "Home - Rettsyndrome.org". www.rettsyndrome.org. Archived from the original on 2016-10-10. Retrieved 2016-10-07.
-  Archived February 8, 2007, at the Wayback Machine
- "Hultin G. Why Celebrate Vegetarian Awareness Month? Food & Nutrition, October 7, 2014, Accessed November 14, 2018". 13 October 2021.
- "Vegetarian Awareness Month: Celebrating Meatless Mindfulness, Oldways website, September 28, 2017, Accessed November 14, 2018".
- "World Vegetarian Day, October 1. North American Vegetarian Society (the North American WVD sponsor explains that "World Vegetarian Day [on] October 1st is the annual kick-off of Vegetarian Awareness Month", accessed November 14, 2018".
- "Palmer S. World Vegetarian Awareness Month. Vegan Outreach website, October 2, 2017, Accessed November 14, 2018". 3 October 2017.
- "October is National Vegetarian Awareness Month. Fix.com. October 1, 2014, Accessed November 14, 2018".
- "Celebrate Vegetarian Awareness Month. Fruits & Veggies: More Matters. Monday, October 14, 2013, at 4:00 am. Accessed November 14, 2018".
- "Gerber J. 9 Easy Wasys to Celebrate Vegetarian Awareness Month. Care2. October 1, 2012. Accessed November 14, 2018". Archived from the original on November 15, 2018. Retrieved November 15, 2018.
- Nivison, Austin (October 30, 2023). "Sports Equinox 2023: NFL, NBA, NHL and MLB games taking place on same day for 30th time in history". CBS Sports.
- "American Archives Month". National Archives. 2017-06-22. Retrieved 2018-09-25.
- "October is Adopt a Shelter Dog Month". ASPCA. Retrieved 2014-10-17.
- "About NCSAM". www.staysafeonline.info. Archived from the original on October 5, 2009.
- "American Pharmacists Month 2011". Pharmacist.com. Archived from the original on October 11, 2007. Retrieved 2011-11-01.
- "Little People of the World".[dead link]
- "Little People of America". Archived from the original on 2014-10-06. Retrieved 2014-09-30.
- "Eczema Awareness Month – National Eczema Association". National Eczema Association. Archived from the original on 2015-05-20. Retrieved 2015-05-19.
- "ADHA – October is National Dental Hygiene Month". Adha.org. Retrieved 2011-11-01.
- "Healthy Lung Month – Lung problems". 5 October 2012.
- "Observing Infertility Awareness Month". Library.adoption.com. Archived from the original on 2008-08-28. Retrieved 2011-11-01.
- "Liver Awareness Month". www.liverfoundation.org. 4 August 2017. Archived from the original on 29 September 2016. Retrieved 6 October 2016.
-  Archived November 21, 2007, at the Wayback Machine
- APTA | National Physical Therapy Month Archived January 5, 2009, at the Wayback Machine
- "Spina Bifida Association – Spina Bifida Association". Sbaa.org. Archived from the original on 2007-10-14. Retrieved 2011-11-01.
- "October is SIDS Awareness Month". www.nichd.nih.gov.
- "National Pizza Month". Pizza.com. Retrieved 2012-10-24.
- "Popcorn Poppin' Month". Popcorn.org. Retrieved 2012-10-24.
- "October is National Pork Month". ThePigSite. 2007-10-02.
- "NOAA Fisheries Celebrates National Seafood Month". NOAA.gov. 2017-10-01. Retrieved 2017-10-09.
- Szoó, Attila (26 October 2020). ""Brussels should pay attention to the Szeklers" – Day of Szekler Autonomy". Transylvania Now.
- "Diversity – UMUC". www.umuc.edu. Archived from the original on 2016-09-19. Retrieved 2016-08-20.
- "October doth before us go (feat. Leisha Stevens)". YouTube. Archived from the original on 2021-12-11. Retrieved 30 September 2021.
- "October doth before us go (feat. Leisha Stevens)". Amazon. Retrieved 30 September 2021.