Meg-John Barker (born 23 June 1974) is a writer, writing mentor, creative consultant, speaker, and independent scholar. They have written a number of anti self-help books on the topics of relationships, sex, and gender, as well as the graphic non-fiction books, Queer: A Graphic History and Gender: A Graphic Guide, and the book The Psychology of Sex. They are the writer of the relationships book and blog Rewriting the Rules, and they have a podcast with sex educator Justin Hancock.

Barker is a full-time writer, as well as being a writing mentor, creative consultant, speaker, and independent scholar. Barker holds a PhD in Psychology from the University of Nottingham, and worked for two decades as an academic psychologist at the Open University in the United Kingdom, and as a psychotherapist specialising in sex, gender, and relationships.

Barker has written and/or edited some of the first academic collections on open non-monogamy, bisexuality, non-binary gender and BDSM. They were editor of the journal Psychology & Sexuality from 2010 to 2017, and lead author of The Bisexuality Report and the BACP document on Gender, Sexual, and Relationship Diversity.