|Country||United States of America|
|• Total||5.4 sq mi (13.9 km2)|
|• Land||5.4 sq mi (13.9 km2)|
|• Water||0.0 sq mi (0.0 km2)|
|• Density||1,800/sq mi (710/km2)|
|Time zone||Eastern (EST) (UTC-5)|
|• Summer (DST)||EDT (UTC-4)|
Timonium is a census-designated place (CDP) in Baltimore County, Maryland, United States. As of the 2010 census it had a population of 9,925. Prior to 2010 the area was part of the Lutherville-Timonium CDP. The Maryland State Fair is held in Timonium each year near Labor Day on the grounds of the former Timonium Race Course, which is an important site along with Pimlico Race Course in northwest Baltimore and Laurel Park in Prince George's County, along with other former tracks at Bowie and Rosecroft in Maryland thoroughbred horse racing traditions.
The town is north of Baltimore City along York Road (Maryland Route 45). It is bordered on the north by Cockeysville, on the south by Lutherville, on the east by Loch Raven Reservoir, and on the west by the Baltimore-Harrisburg Expressway, Interstate 83, with the Greenspring and Worthington Valleys beyond. Ridgely Road forms the boundary between Timonium and Lutherville, while Padonia Road separates Timonium from Cockeysville.
Timonium is located in the Piedmont region of the United States, and lies in the transition zone between the Humid subtropical climate zone to the south and the humid continental climate to the north, with hot and humid summers leading into winters that are cold but not extreme by American standards. The average annual snowfall is 25 inches (64 cm) and average annual rainfall is 42 inches (107 cm).
The name Timonium is believed to be related to the palace built by, Marc Antony in Alexandria, which in turn was named after the misanthropic figure of Timon of Athens. In local Maryland legend, the land was a plantation that a grieving widow renamed as "Timonium." 
Major roads in the Timonium area include:
- Deereco Road
- Dulaney Valley Road (MD-146)
- Pot Spring Road
- Timonium Road
- York Road (MD-45)
- Padonia Road
- Beaver Dam Road
The Maryland Transit Administration's light rail line has two stops in Timonium area: Timonium Business Park and Timonium. In addition, bus routes 8 and 9 provide regular service along the York Road corridor.
- Spiro T. Agnew, former U.S. Vice President and Governor of Maryland (plus Baltimore County Executive), buried in Timonium
- Mark Belanger, former Baltimore Orioles shortstop
- William C. Bilo, United States Army Brigadier General and Deputy Director of the Army National Guard
- Beth Botsford, swimmer
- Robert Ehrlich, 60th Governor of Maryland. He was a resident of Timonium while serving in Congress as a Representative in the House of Representatives (although raised in Arbutus which he often cited).
- Jim Gentile, former Baltimore Orioles first baseman.
- Pam Shriver, tennis player.
- Don Shula, former Baltimore Colts player and coach in the 1960s, later famous coach of the Miami Dolphins, undefeated champions in 1972 in the National Football League, member of the Pro Football Hall of Fame.
- Dick Szymanski, former Baltimore Colts player.
- Gus Triandos, former Baltimore Orioles catcher in the 1950s; Triandos Drive is named in honor of him.
- Johnny Unitas, former Baltimore Colt quarterback and Hall of Famer in the National Football League; buried at Dulaney Valley Memorial Gardens.
- Cheryl Wheeler, singer-songwriter.
- All Time Low, Rock/Pop-Punk Band.
- Public schools
- Pinewood Elementary School
- Pot Spring Elementary School
- Timonium Elementary School
- Ridgely Middle School (in Lutherville)
- Dulaney High School
- Padonia Elementary
- Riderwood Elementary
- "Profile of General Population and Housing Characteristics: 2010 Demographic Profile Data (DP-1): Timonium CDP, Maryland". U.S. Census Bureau, American Factfinder. Retrieved February 23, 2012.
- "US Gazetteer files: 2010, 2000, and 1990". United States Census Bureau. 2011-02-12. Retrieved 2011-04-23.
- "Geographic Identifiers: 2010 Demographic Profile Data (G001): Timonium CDP, Maryland". U.S. Census Bureau, American Factfinder. Retrieved February 23, 2012.
- Barone, Michael; Ujifusa, Grant (1999). The Almanac of American Politics 2000. National Journal Group Inc. p. 748.