Biphobia is aversion toward bisexuality and toward bisexual people as a social group or as individuals. It can take the form of denial that bisexuality is a genuine sexual orientation, or of negative stereotypes about people who are bisexual (such as the beliefs that they are promiscuous or dishonest). People of any sexual orientation can experience or perpetuate biphobia, and it is a source of social discrimination against bisexual people.

Lesbophobia (sometimes lesbiphobia) comprises various forms of negativity towards lesbians as individuals, as couples, or as a social group. Based on the categories of sex, sexual orientation, lesbian identity, and gender expression, this negativity encompasses prejudice, discrimination, and abuse, in addition to attitudes and feelings ranging from disdain to hostility. As such, lesbophobia is sexism against women that intersects with homophobia and vice versa.

Transphobia is a range of negative attitudes, feelings or actions toward transgender or transsexual people, or toward transsexuality. Transphobia can be emotional disgust, fear, violence, anger or discomfort felt or expressed towards people who do not conform to society's gender expectations. It is often expressed alongside homophobic views and hence is often considered an aspect of homophobia. Transphobia is a type of prejudice and discrimination similar to racism and sexism, and transgender people of color are often subjected to all three forms of discrimination at once.

Child victims of transphobia experience harassment, school bullying, and violence in school, foster care, and social programs. Adult victims experience public ridicule, harassment including misgendering, taunts, threats of violence, robbery, and false arrest; many feel unsafe in public. A high percentage report being victims of sexual violence. Some are refused healthcare or suffer workplace discrimination, including being fired for being transgender, or feel under siege by conservative political or religious groups who oppose laws to protect them. There is even discrimination from some people within the movement for the rights of gender and sexual minorities.

Besides the increased risk of violence and other threats, the stress created by transphobia can cause negative emotional consequences which may lead to substance abuse, running away from home (in minors), and a higher rate of suicide.

In the Western world, there have been gradual changes towards the establishment of policies of non-discrimination and equal opportunity. The trend is also taking shape in developing nations. In addition, campaigns regarding the LGBT community are being spread around the world to improve acceptance; the "Stop the Stigma" campaign by the UN is one such development.

Homophobia encompasses a range of negative attitudes and feelings toward homosexuality or people who are identified or perceived as being lesbian, gay, bisexual or transgender (LGBT). It has been defined as contempt, prejudice, aversion, hatred or antipathy, may be based on irrational fear, and is often related to religious beliefs.

Homophobia is observable in critical and hostile behavior such as discrimination and violence on the basis of sexual orientations that are non-heterosexual. Recognized types of homophobia include "institutionalized" homophobia, e.g. religious homophobia and state-sponsored homophobia, and "internalized" homophobia, experienced by people who have same-sex attractions, regardless of how they identify.

Negative attitudes toward identifiable LGBT groups have similar yet specific names: lesbophobia is the intersection of homophobia and sexism directed against lesbians, biphobia targets bisexuality and bisexual people, and transphobia targets transgender and transsexual people and gender variance or gender role nonconformity. According to 2010 Hate Crimes Statistics released by the FBI National Press Office, 19.3 percent of hate crimes across the United States "were motivated by a sexual orientation bias." Moreover, in a Southern Poverty Law Center 2010 "Intelligence Report" extrapolating data from fourteen years (1995–2008), which had complete data available at the time, of the FBI's national hate crime statistics found that LGBT people were "far more likely than any other minority group in the United States to be victimized by violent hate crime."

The term "homophobia" and its usage have been criticized by several sources as unwarrantedly pejorative

During the year prior to the 2015 U.S. survey, 59 percent of respondents reported avoiding using a public restroom out of fear of violence or harassment. 32 percent limited the amount they ate or drink in order to avoid using a public restroom. Eight percent reported suffering a urinary tract infection, kidney infection, or other kidney problem as a result of avoiding public restrooms.

Thirty-three percent reported having negative experiences with a healthcare professional related to being transgender, such as verbal harassment or denial of treatment. 23 percent reported that they did not seek treatment for a condition out of fear of being mistreated, while 33 percent did not seek treatment because they were unable to afford it.

During the month prior to the survey, 39 percent of American transgender people experienced major psychological distress, compared to 5 percent of the general population of the United States. 40 percent had attempted suicide at some point in their life, compared to 4.6 percent of the American population. Family and community support were correlated with far lower rates of suicide attempts and of major psychological distress.

A study conducted on transgender women of color in San Francisco has shown a higher correlation between transphobia and risk of transgender women engaging in HIV risk behavior. The study shows that the transgender youth face social discrimination, and they may not have a social role model. The young adults in this group have shown a higher risk of engaging in unprotected receptive anal intercourse when the exposure to transphobia is high. Therefore, as per the study shows a correlation between transphobia and high risk of HIV.

While some people use only the more general term "homophobia" to describe this sort of prejudice or behavior, others believe that the terms "homosexual" and "homophobia" do not adequately reflect the specific concerns of lesbians, because they experience the double discrimination of both homophobia and sexism. Similarly, bisexual women may prefer to use the term biphobia to refer to prejudice or abuse that they encounter which is based on their bisexual identity or behaviour, and people who identify as transgender often prefer to use the word transphobia.

"Biphobia" is a portmanteau word patterned on the term "homophobia". It derives from the English neo-classical prefix "bi-" (meaning "two") from "bisexual" and the root "-phobia" (from the , "phóbos", "fear") found in "homophobia". Along with "transphobia" and "homophobia", it is one of a family of terms used to describe intolerance and discrimination against LGBT people. The adjectival form "biphobic" describes things or qualities related to biphobia, and the less-common noun "biphobe" is a label for people thought to harbor biphobia.

"Biphobia" need not be a phobia as defined in clinical psychology (i.e., an anxiety disorder). Its meaning and use typically parallel those of "xenophobia".

Although sexual attitudes tracing back to Ancient Greece (8th to 6th centuries BC to the end of antiquity (ca. 600 AD)) have been termed homophobia by scholars, the term itself is relatively new, and an intolerance towards homosexuality and homosexuals grew during the Middle Ages, especially by adherents of Islam and Christianity.

Coined by George Weinberg, a psychologist, in the 1960s, the term "homophobia" is a blend of (1) the word "homosexual", itself a mix of neo-classical morphemes, and (2) "phobia" from the Greek φόβος, Phóbos, meaning "fear" or "morbid fear". Weinberg is credited as the first person to have used the term in speech. The word "homophobia" first appeared in print in an article written for the May 23, 1969, edition of the American pornographic magazine "Screw", in which the word was used to refer to heterosexual men's fear that others might think they are gay.

Conceptualizing anti-LGBT prejudice as a social problem worthy of scholarly attention was not new. A 1969 article in "Time" described examples of negative attitudes toward homosexuality as "homophobia", including "a mixture of revulsion and apprehension" which some called "homosexual panic". In 1971, Kenneth Smith used "homophobia" as a personality profile to describe the psychological aversion to homosexuality. Weinberg also used it this way in his 1972 book "Society and the Healthy Homosexual", published one year before the American Psychiatric Association voted to remove homosexuality from its list of mental disorders. Weinberg's term became an important tool for gay and lesbian activists, advocates, and their allies. He describes the concept as a medical phobia:

In 1981, "homophobia" was used for the first time in "The Times" (of London) to report that the General Synod of the Church of England voted to refuse to condemn homosexuality.