The 69-year-old actress was contemplating retirement due to hip issues when her agent accepted the role without her initial consultation.
Hamilton will portray Dr Kay, the head scientist of a military division in Hawkins, who possesses a private and ruthless agenda.
She described her character as having “deeper personal desires” and being “ruthless”, which she found enjoyable to play.
The first half ofStranger Things season five is set to debut on Netflix in the UK on 27 November, with subsequent episodes arriving on Boxing Day and New Year’s Day 2026.