Flag Day (disambiguation)
Flag Day is a day to fly a flag of a certain area or a day set aside to honor an event specifically involving a national flag.
Flag Day may also refer to:
National days
- Flag Day (Albania)
 - Flag Day (Argentina)
 - Flag Day (Australia)
 - National Flag of Canada Day
 - Armed Forces Flag Day, celebrated in India
 - Flag Day (Mexico)
 - Day of the National Flag (Russia)
 - Day of the National Flag (Ukraine)
 - Flag Day (United Arab Emirates)
 - Flag Day (United States)
 
Other uses
- Flag day (computing), a large change
 - Flag Day (film), a 2021 film by Sean Penn
 - Flag Day (Hong Kong), a day for charity fundraising - also practised in Singapore
 - "Flag Day" (song), a song by The Housemartins