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.

The word "transphobia" is a classical compound patterned on the term "homophobia", sharing its second component "-phobia" from the , "phóbos", "fear". The first component is the neo-classical prefix "trans-" from "transgender" (originally meaning "across, on the far side, beyond"). Along with "lesbophobia", "biphobia", "homophobia" and "transphobia" are members of the family of terms used when intolerance and discrimination is directed toward LGBT people.

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

The adjectival form "transphobic" describes things or qualities related to transphobia, and the noun "transphobe" denotes someone who harbors transphobia.