This chapter deals with sex discrimination law under the Equality Act. It discusses the historical and legal background of sex discrimination law, protected characteristics and prohibited conduct on grounds of sex discrimination. Sex discrimination is symmetrical in that it can be claimed by both men and women. Direct sex discrimination cannot be justified unless there is an occupational requirement while indirect sex discrimination can be objectively justified. A person who has been treated less favourably for claiming sex discrimination or giving evidence in such a matter can claim victimisation. A person can claim harassment, and sexual harassment is also specifically outlawed in the Equality Act. The chapter also discusses dress codes.