Illinois is seen as one of the most progressive states in the U.S. in regard to lesbian, gay, bisexual, transgender, and queer (LGBTQ) rights and often viewed as one of the most liberal states in the Midwestern United States. Same-sex sexual activity has been legal since 1962, after Illinois became the first U.S. state to repeal its sodomy laws. Same-sex marriage was banned by statute in 1996, but has since been legalized after a law allowing such marriages was signed by Governor Pat Quinn on November 20, 2013 and went into effect on June 1, 2014. Since January 1, 2015 the Constitution of Illinois legally prevents sexual orientation discrimination on the right to vote within Illinois.

Civil unions have been recognized since 2011, and same-sex couples are also allowed to adopt. Additionally, discrimination on the basis of sexual orientation and gender identity is banned in employment, housing, credit and public accommodations, and conversion therapy on minors has been outlawed since 2016.

Chicago has a vibrant LGBTQ community. The first pride parade took place in 1970, a year after the Stonewall riots. Since 2013, the Chicago Pride Parade has attracted about 1 million attendees each year. 2019 polling from the Public Religion Research Institute showed that 74% of Illinois residents supported anti-discrimination legislation protecting LGBTQ people.

Law regarding same-sex sexual activity In 1795, Illinois as part of the Northwest Territory inherited the English "buggery" law, which punished sodomy with death. In 1819, after statehood, it enacted its own statute which outlawed sodomy with one to five years' imprisonment, a fine of 100-500 dollars and between 100 and 500 lashes. A change in 1874 resulted in the maximum imprisonment penalty being set at 10 years. The first reported sodomy case occurred in 1897 in Honselman v. People where the Supreme Court of Illinois ruled that fellatio (oral sex), whether heterosexual or homosexual, was a violation of the sodomy law; the first such case in the United States. In 1913, in People v. Smith, the court held that cunnilingus was not a "crime against nature", stating that "without a male sexual organ, there could be no sodomy". In 1950, in People v. Whitham, the court rejected the contentions of a heterosexual man that sodomy could only be accomplished between same-sex partners.

In 1938, the Illinois General Assembly passed a "psychopathic offender" law, under which anyone suffering from a "mental disorder" and who had "criminal propensities to the commission of sex crimes" was considered and legally labelled a "sexual psychopath". The law was upheld by the Illinois Supreme Court in 1943 in People v. Sims. The statute was amended in 1951 to permit examination of any prisoner "at suitable intervals" to see if he or she "has become a criminal sexual psychopath." It also provided that any prisoner convicted of certain crimes, including the "crime against nature", be examined upon release from prison to see if the person was a "criminal sexual psychopath". The law was reportedly widely used against offenders who had engaged in consensual sexual activity.

On July 28, 1961, Illinois enacted a new state law code, that became effective on January 1, 1962, and eliminated the state's sodomy laws. It was the first state to eliminate its sodomy laws and established an age of consent of 18. However, a major oversight was soon discovered, as the laws against the "infamous crime against nature either with man or beast" were not included in the Criminal Code of 1961, meaning that for a brief period of time, bestiality was technically legal in the state of Illinois. The code also made it a crime to commit a "lewd fondling or caress of the body of another person of the same sex" in a public place. In 1963, the General Assembly passed a new law that changed the words "the same sex" to "either sex". In 1984, the "lewd fondling or caress" law was repealed and the age of consent was lowered to 16. On January 1, 2012, the age of consent was raised to 17.

In 1970, Illinois voters approved a constitutional amendment which grants people the right "to be secure in their persons, houses, papers and other possessions against unreasonable searches and seizures, invasions of privacy or interceptions of communications".

Recognition of same-sex relationships

Marriage

SB 1773 SB 1773, introduced by Representative Tom Johnson in 1996, amended the Illinois Marriage and Dissolution of Marriage Act to preclude out-of-state recognition of same-sex marriage and reinforce the state's marriage ban in light of Baehr v. Lewin in Hawaii. It was vigorously opposed, with 12,000 letters being written by clergymen, parishioners and other citizens of all faiths. Representatives Ronen, Schakowsky and Currie led the futile effort to defeat the bill, with Ronen stating at one point, "...don't delude yourself, to think that you are doing God's work. I would remind you that a long list of clergy and religious groups have forcefully spoken out against this Bill." The bill passed 42–9 in the Senate and 87–13 (with 6 abstentions) in the House. The bill was signed in May 1996.

SB 10 (Marriage) Same-sex marriage was legalized via statute in November 2013, after the Illinois House of Representatives narrowly approved same-sex marriage legislation by 61 votes to 54 (achieving the 60 vote required threshold). The Illinois Senate subsequently approved the legislation 32–21 (achieving the 30 vote required threshold). Barack Obama (then-President of the United States and former Senator of Illinois) welcomed the bill, stating on his Instagram page: "Congratulations, Illinois. Love is love."Barack Obama on Instagram: “Congratulations, Illinois. #LoveIsLove” (November 6, 2013) The bill was signed by Democratic governor Pat Quinn on November 20, and it went into effect June 1, 2014. In July 2021, the governor of Illinois signed a bill into law to legally provide individuals a gender-neutral marriage certificate available. In May 2023, both houses of the Illinois Legislature passed a bill to formally repeal three marriage law sections (dating back to 1972) regarding getting married within Illinois from other jurisdictions that makes a marriage within Illinois "null and void" if the marriage is not recommended, licensed or recognized from that particular jurisdiction by error or bad judgement. The governor of Illinois signed the bill in 2023, making it effective in 2024.

Civil unions On January 31, 2011, Governor Pat Quinn signed legislation that recognizes same-sex civil unions, effective from June 1, 2011. The law allows the state to recognize same-sex marriages performed outside of Illinois as the equivalent of an Illinois civil union. If a person undergoes sex reassignment surgery, the marriage is still recognized by the state, even though the parties to the marriage are of the same sex.

Illinois has provided benefits to same-sex partners of state employees since 2006.National Conference of State Legislatures: "States offering benefits for same-sex partners of state employees" , accessed April 16, 2011

In 2012, legislation to repeal the state's recognition of same-sex civil unions was introduced in the House of Representatives, but was defeated.Chicago Tribune: Rex W. Huppke, "Same-sex marriage supporters take their fight to Illinois courts," May 29, 2012, accessed May 30, 2012

Lawsuits In May 2012, Lambda Legal and the American Civil Liberties Union filed lawsuits in state court challenging the refusal of the Cook County clerk's office to issue marriage licenses to same-sex couples. Both contended that the Illinois Marriage and Dissolution of Marriage Act violated the Illinois Constitution's guarantees of equal protection and due process.Minnesota Public Radio: Sophia Tareen, "ACLU challenges Ill. marriage law," May 30, 2012, accessed May 30, 2012 These lawsuits have since been abandoned due to the State General Assembly passing a same-sex marriage law in November 2013.

On February 21, 2014, a federal judge authorized Cook County to issue marriage licenses to same-sex couples without waiting for the Illinois statute legalizing same-sex marriage to take effect on June 1, and the county clerk began issuing licenses immediately.

Discrimination protections and anti-bullying laws

Since June 1, 2006, Illinois has protected LGBT persons from unfair discrimination. The state's anti-discrimination law applies to the areas of employment, housing, public accommodations and credit, and forbids discrimination on the grounds of "race, color, religion, sex, national origin, ancestry, age, order of protection status, marital status, physical or mental disability, military status, sexual orientation, pregnancy, or unfavorable discharge from military service". The definition of sexual orientation explicitly includes gender identity. The Illinois Human Rights Act states: "'Sexual orientation' means actual or perceived heterosexuality, homosexuality, bisexuality, or gender-related identity, whether or not traditionally associated with the person's designated sex at birth. 'Sexual orientation' does not include a physical or sexual attraction to a minor by an adult."

The city of Chicago enacted an anti-discrimination ordinance of its own in 1988.

In 2014, Illinois expanded its anti-bullying laws to make them inclusive of LGBTQ people. Illinois law prohibits bullying based on race, color, religion, sex, national origin, ancestry, age, marital status, physical or mental disability, military status, sexual orientation, gender identity or expression, unfavorable discharge from military service, association with a person or group with one or more of the aforementioned actual or perceived characteristics, or any other distinguishing characteristic. The legislation requires school districts, charter schools and non-sectarian private schools to strengthen their anti-bullying policies in order to provide a safe learning environment for all students, including investigating reports of bullying, protecting the privacy of students, prohibiting false accusations and training staff to properly address incidents.

In June 2018, the Illinois General Assembly passed a bill to repeal the "15 or more employees in a company or business" loophole, which had exempted businesses with less than 15 employees from the state's anti-discrimination law.Bill Status of HB4572 100th General Assembly Illinois General Assembly In August 2018, Governor Bruce Rauner vetoed the bill, and no attempts to override his veto were undertaken before the General Assembly adjourned sine die in January 2019. A similar bill to repeal the 15 employee loophole passed both chambers of the General Assembly in May 2019, was signed into law by Governor J. B. Pritzker in August 2019 and went into effect on July 1, 2020.

In May 2019, the General Assembly passed a bill, passing the House by a vote of 115–0 and the Senate by 54 votes to 0, to add "sexual orientation" as a prohibited ground of discrimination in jury selections. Governor J. B. Pritzker signed the bill into law in August 2019, and it went into effect on January 1, 2020.

Illinois corporate boards In June 2021, a bill passed the Illinois General Assembly to provide LGBTQ inclusion and quotas on corporate boards within Illinois. The governor of Illinois signed the bill into law in August 2021 and will go into effect from January 1, 2022.

Domestic violence The Illinois Domestic Violence Act, which protects people who share or used to share a dwelling or a "dating relationship" with their abusers, is written in gender-neutral language and is applicable to same-sex partners.Illinois Domestic Violence Act of 1986. 750 ILCS 60/103(6).

Illinois school students with trauma and book protection