Vernon County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 30,714. Its county seat is Viroqua.
 Vernon County was renamed from Bad Ax County on March 22, 1862. Bad Ax County had been created on March 1, 1851, from territory that had been part of Richland and Crawford counties. The name Vernon was chosen to reflect the county's green fields of wheat and to evoke Mount Vernon.
 According to the U.S. Census Bureau, the county has a total area of 816 square miles (2,110 km2), of which 792 square miles (2,050 km2) is land and 25 square miles (65 km2) (3.0%) is water.
 As of the census of 2020, the population was 30,714. The population density was 38.8 people per square mile (15.0 people/km2). There were 13,813 housing units at an average density of 17.5 units per square mile (6.8 units/km2). The racial makeup of the county was 95.4% White, 0.4% Black or African American, 0.3% Asian, 0.2% Native American, 0.8% from other races, and 2.9% from two or more races. Ethnically, the population was 1.5% Hispanic or Latino of any race.
 As of the census of 2000, there were 28,056 people, 10,825 households, and 7,501 families residing in the county. The population density was 35 people per square mile (14 people/km2). There were 12,416 housing units at an average density of 16 units per square mile (6.2 units/km2). The racial makeup of the county was 98.81% White, 0.06% Black or African American, 0.15% Native American, 0.21% Asian, 0.01% Pacific Islander, 0.27% from other races, and 0.48% from two or more races. 0.66% of the population were Hispanic or Latino of any race. 38.3% were of Norwegian, 26.9% German, 6.4% Irish and 6.1% English ancestry. 90.9% spoke English, 3.5% German, 1.8% Norwegian, 1.2% Pennsylvania Dutch and 1.0% Spanish as their first language.
 There were 10,825 households, out of which 31.50% had children under the age of 18 living with them, 58.70% were married couples living together, 6.80% had a female householder with no husband present, and 30.70% were non-families. 26.70% of all households were made up of individuals, and 13.70% had someone living alone who was 65 years of age or older. The average household size was 2.55 and the average family size was 3.11.
 In the county, the population was spread out, with 27.40% under the age of 18, 6.80% from 18 to 24, 25.30% from 25 to 44, 23.50% from 45 to 64, and 17.00% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 97.70 males. For every 100 females age 18 and over, there were 95.60 males.
 In 2017, there were 434 births, giving a general fertility rate of 90.5 births per 1000 women aged 15–44, the fourth highest rate out of all 72 Wisconsin counties. Of these births, 123 occurred at home, second only to Clark County which had 184 home births.
 In 2010, the largest religious groups by reported number of adherents were ELCA Lutheran at 6,735 adherents, Catholic at 3,060 adherents, Amish at 2,786 adherents, United Methodist at 1,533 adherents, Wisconsin Synod Lutheran at 1,402 adherents, and Non-denominational Christian at 766 adherents.
 Religion in Vernon County,according to ARDA (2020) 
 The county is home to the headquarters of Organic Valley, the world's largest cooperative of family farmers.
 Vernon County is home to multiple county and state parks. The Kickapoo Valley Reserve, an 8600-acre natural reserve, is between the villages of La Farge and Ontario. Wildcat Mountain State Park is also in the county.
 Vernon County had been a Democratic-leaning county since the 1988 presidential election, but Republican Donald Trump won a plurality of the vote in 2016 and a majority of the vote in 2020.
 43°35′N 90°50′W﻿ / ﻿43.59°N 90.83°W﻿ / 43.59; -90.83