|• Founder||William Berczy|
|Elevation||200 m (700 ft)|
|Time zone||Eastern Standard Time (EST) (UTC-5)|
|• Summer (DST)||Eastern Daylight Time (EDT) (UTC-4)|
|Forward sortation area||L3P, L3R, L3S, L6B, L6C, L6E and L6G|
|Area code(s)||905 and 289|
Unionville is a suburban village in Markham, Ontario, Canada. It is located 33 km northeast of downtown Toronto and 4 km east of southern Richmond Hill. The boundaries of Unionville are not well-defined, as it is not a municipal entity, but several communities claim to be part of it.  
However, Unionville was founded north of 16th in 1794, and many of the farms on and around Woodbine Ave. on its western edge considered themselves part of Unionville. The Unionville Ratepayers Association designated a relatively new road, Rodick Road, as its western boundary, in the 1980s. Main Street, which was Kennedy Road in the mid-to-late 20th century, runs through Unionville while the new Kennedy runs 300 m to the east.
The population of Unionville is about 80,000. Unionville is composed of many neighbourhoods including the historic centre of Unionville, Upper and South Unionville, Angus Glen, Cachet,Buttonville and Victoria Square. Unionville is said to be one of the most affluent areas in the Greater Toronto Area with an average household income of $127,900. Rouge River runs north of the central part of Unionville and to the southeast. The highway (Highway 404) is to the west, the nearest interchange with the Highway 407 is 2 km south on Kennedy Rd. The population lives in almost all parts of Unionville except for the south central industrialized area, which is now slated for massive intensification.
Tourism is a major part of Unionville's economy. The historic village or downtown section of Unionville is typical of a small town that developed over a century or so starting in the early 1840s (when Ira White erected his Union Mills) through the middle to late 20th century. The historic Main Street Unionville attracts thousands of visitors each year — as of 2006 it boasted nine restaurants, including three pubs. Main Street (originally the laneway from the village's first grist mill) also has a number of "century homes" dating back to the 19th century. Each year, thousands of people visit Unionville during the Unionville Festival.
Most of the historic buildings in Unionville are included in List of historic buildings in Markham, Ontario.
Once surrounded by farmlands, the village is now surrounded by suburban housing tracts. During the revival period in the 1970s a ban was placed on development for 25 years, but that time has now passed.
There is concern about how the village is changing, with farm lands being converted to housing developments, and heritage buildings being replaced with new homes.
The Beckett Farm was the last remaining farmland in Upper Unionville. The farm was a landmark on 16th Avenue, with its wide open space and picturesque barn and silo, a reminder of Markham's agricultural past. This 204-acre landmark is now being developed for a new subdivision, planned to be partially completed by 2014. There is still some farmland north part of Unionville part of the city of Markham's Greenbelt just North of Major MacKenzie Dr. just past the Victoria Manor and Jennings Gates subdivisions to the Rouge River past Kennedy Road in the Hamlets of Cashel, Victoria Square, and Almira.
Unionville was a "Police Village" within what was then called Markham Township within York County until the end of 1970, at which time York County was reorganized into the Regional Municipality of York by Provincial Statute. Unionville (and all of the nine other Police Villages in the county) were abolished. Markham Township was also abolished, some of its lands were annexed by neighbouring Richmond Hill and Whitchurch–Stouffville, and the remainder was annexed by the Town of Markham, an urban area 2.5 miles east of Unionville, now the City of Markham. The town and the township were named after two different people named "Markham". The name "Unionville" remained a valid postal address until the early 1990s at which time most addresses were changed to "Markham". In 2009, Markham Town Council reinstated the name "Unionville" for that portion of postal addresses within its Ward 3, which lies between Warden, 16th, McCowan and the 407. However, the Post Office used "Unionville" as the postal address for a larger delivery area that included the farms that it considered to be "in Unionville". Unionville's historical boundaries, therefore, maybe based on the historic Post Office delivery area for the name "Unionville". These varied somewhat over a century and a half, as neighbouring post offices came and went, but at some time or other the following areas had a "Unionville" address:
- Hwy 7 & southward: all of the area north of Steeles between Woodbine on the west & McCowan on the east, including both sides of Woodbine, McCowan & Hwy 7.
- North of Hwy 7: all of the area to 19th Avenue between Warden on the west & McCowan on the east, including both sides of Woodbine, McCowan & 19th.
Unionville also extended westward on both sides of 19th Avenue to the 404.
Since January 1, 1971, Unionville has had no legal municipal boundary.
Markham changed its status from town to city on July 1, 2012.
In the 1960s, major housing development came to Unionville and is still ongoing. Having old buildings available at low cost, a number of antique stores sprang up and for a while in the 1970s Unionville ranked high on the list of places to go to get antiques. After the commitment to a bypass was realised, in the 1970s, entrepreneurs appeared. The Old Country Inn opened for business and Old Firehall Sports brought a new clientele to the village. Over the next decades, the antique places disappeared being replaced by high-end antique and replica outlets, restaurants, pubs, and clothing establishments. Tourism was born. Starbucks appeared in the late 1990s. Many of the buildings have been spruced up, extended and upgraded to meet this new reality. The old original road, to the immediate east of Main Street, once considered to be swamp land, has been converted to a large parking lot.
Walking paths through the local conservation lands connect directly to the village roads, one of the most used being the path around Toogood Pond, named after the Toogood family - the pond was originally the mill pond that powered the grist mill in the 1840s. In the early 20th century the pond was called Willow Pond or Willow Lake and was the home to several small summer cottages on north Main Street. Some had been cottages, for grist mill workers, in their earliest incarnation. Those cottages evolved into homes by the middle of the century, but are almost all gone now being replaced by large spacious expensive homes.
The Varley Art Gallery now stands at the north end of the commercial Main Street and is rapidly becoming a gallery of wide renown. It was started with the contributions of Mrs. McKay, who had supported Group of Seven artist Fred Varley for the later part of his life. Living in her home on Main Street Unionville, he did several paintings that are now part of the Art Gallery collection and the home is now part of the Art Gallery's holdings, being used for small art shows on a regular basis.
In the mid-1990s until the summer of 1999, Highway 407 was under construction. It is Ontario's first toll road and was first opened the summer of 1998 at McCowan Road. It was later extended to Brock Road.
The Unionville Arms, a well-known pub, burnt down on November 30, 2007. It had been in business for 19 years prior. The building itself was over a century old. The legendary building caught fire in the morning, supposedly due to a combination of faulty kitchenware and wiring, and the century-old insulation. The fire was put out three hours later. No one was hurt. The Arms reopened in very much its original appearance, towards the end of December 2008. Another popular pub is Jake's, housed in what used to be the funeral parlour.
A new library, the Markham Public Library (Unionville branch), was completed in 1984, replacing the older Unionville Library, which was renamed the "Old Library Community Centre", and is now used for dance classes, meetings, and a church. The new library occupies 14,000 sq. ft., and is based on a traditional village square surrounded by eight "houses" of books expressed on the exterior as postmodern Victorian dormers. The library, which contains approximately 100,000 books and audiovisual materials, was designed by architect Barton Myers.
The Stiver Mill is a historic building located near the railway tracks on Main Street Unionville. The building was restored in 2014 and is now a community centre. The area around the building has also been modernized for accessibility to both the centre and the train station next to it. 
The Unionville Festival was first organized in 1969 to raise awareness and money to fight the provincial plan to run a four lane road up the middle of the town and thus destroying it. An interest in history, spurred by the Canadian Centennial Year in 1967, awoke the longtime residents and the new subdivision residents. Slowly, local politicians got on board, and a plan was drawn up to divert the road to the east of the historic town center (now known as Kennedy Road). Today the festival continues to offer visitors access to handcrafts, small vendors, live music and community groups. Virtually none of the businesses from the mid-20th century still exist, having been replaced by restaurants and tourist outlets.
The Unionville Business Improvement Area and its merchants, organize and operate numerous, year-round, admission free, festivals and events. The Merchants of Main Street Unionville BIA is the business association on Main Street Unionville, composed of volunteers from the business community, who work to preserve and promote the historical village of Unionville.
The Unionville BIA's Heritage Committee has seen its volunteers research and produce a self-guided walking tour. They also offer the official walking tours of Main Street Unionville.
Unionville is, or is considered by some to be, within the following administrative units:
- Ward 3, represented by Councilor Don Hamilton
- Ward 4, represented by Councilor Carolina Moretti (see discussion of boundaries above)
- Ward 6, represented by Councilor Alan Ho (see discussion of boundaries above)
- Markham—Unionville, provincial electoral riding, represented by Michael Chan (Liberal)
- Markham—Unionville, federal electoral riding, represented by John McCallum (Liberal)
- Markham, Ontario - mayor Frank Scarpitti
- Regional Municipality of York, regional council chaired by Bill Fisch
- All Saints Catholic Elementary School
- Buttonville Public School
- Bill Crothers Secondary School
- Coledale Public School
- Sainte-Marguerite-Bourgeoys French Catholic Elementary School
- Markville Secondary School
- John XXIII Catholic Elementary School
- Parkview Public School
- St. Matthew Catholic Elementary School
- St. Justin Martyr Catholic Elementary School
- Unionville High School
- Unionville Meadows Public School
- Unionville Public School
- William Berczy Public School
- St. Augustine Catholic High School
Unionville has a number of regular events ongoing throughout the year. Dates for these can be found on the relevant web sites. Here is a sampling:
- Unionville Village Festival - first weekend of June
- Unionville Heritage Festival - Labour Day
- Olde Tyme Christmas Candlelight Parade - first Friday of December
- Olde Tyme Christmas Breakfast with Santa - morning after the Parade
- Canada Day - July 1
- Markham Jazz Festival - August
- Thursday Nights at the Bandstand - all summer long
- Doors Open Markham - usually autumn
- Remembrance Day at the Cenotaph - Nov. 11
- Hayden Christensen of Star Wars fame attended Unionville High School.
- Emmanuelle Chriqui - Canadian actress who appeared in the television series Entourage and the films On the Line, Snow Day, and In the Mix.
- Anna Russell - English–Canadian singer and comedienne - Anna Russell Way is named after her.
- Steven Stamkos a Canadian ice hockey player of the Tampa Bay Lightning.
- Paul Poirier a figure skater. Competed in 2010 Vancouver Winter Olympics.
- Howie Lee a Canadian ice hockey player who was a member of the Kitchener-Waterloo Dutchmen who won the bronze medal for Canada in ice hockey at the 1956 Winter Olympics.
- Joe Bowen - Toronto Maple Leafs broadcaster.
- James Duthie - TSN Hockey analyst.
- John Paul Morrison - inventor/discoverer of Flow-based programming.
- Ken Pereira - field hockey midfielder.
- Bob Beckett - former Canadian ice hockey centre.
- Andrea Beck - Montreal-born author best known for her Elliot Moose books.
- Donald Deacon - Deacon, OC, O.PEI, MC (1920 - 2003) was a Canadian politician, businessman and volunteer. He was made an officer of the Order of Canada in 2003.
- Marc Bendavid - Canadian film, television and stage actor.
- Gillian Apps - women's ice hockey player. She is the granddaughter of Hockey Hall of Fame member Syl Apps and the daughter of former National Hockey League player Syl Apps, Jr. and his wife Anne.
- John Armstrong - Canadian ice hockey centre.
- "Markham Wards". Retrieved 30 May 2012.
- Hsieh, Tiffany (7 July 2011). "Will the real Unionville please stand up?". Economist and Sun. Retrieved 30 May 2012.
- "Unionville Festival". Retrieved 30 May 2012.
- "Unionville's Geographical Boundary". Retrieved 31 May 2012.
- "Markham to change from town to city". CBC News, May 30, 2012.
- "Toogood Pond Park". Retrieved 30 May 2012.
- "STIVER MILL". Markham. The Corporation of the City of Markham. Retrieved 9 June 2015.
|Wikimedia Commons has media related to Unionville, Ontario.|
|Wikivoyage has a travel guide for Unionville, Ontario.|
- Unionville 150th: Origins of a Community
- Main Street Weather: Local conditions/forecasts, radar, lightning detection, webcam etc.
- Unionville Villagers Association
- Unionville Ratepayers Association
- Unionville Historical Society
- Unionville BIA
|Richmond Hill||Raymerville - Markville East|