Gaius Helen Mohiam, is a fictional character featured in the novel Dune by Frank Herbert. She is the Bene Gesserit Reverend Mother who trained Lady Jessica during her youth and two decades later and tested the young Paul Atreides before his departure for Arrakis.

She holds to his throat a Gom J'bar, which, she says, "kills only animals." The test was to discover whether Paul was "truly human" by trial of pain. The pain inflicted when Paul put his hand in the box was caused by nerve induction and clearly drains an incredible amount of energy from the Reverend Mother.