Nxivm founder Keith Raniere was convicted last year of racketeering, sex trafficking, child pornography possession and other crimes.
As leader of the group he recruited women as slaves and forced them to have sex with him.
Prosecutors said the 60 year old should spend his life behind bars for the "immeasurable damages" he caused to victims of the cult.
District Judge Nicholas Garaufis also fined Raniere $1.75m (£1.34m) at the sentencing hearing in Brooklyn on Tuesday.
