Isaac Dan der Grimnebulin is a human scientist, and one of the main characters in Perdido Street Station (novel). He was formerly a professor at New Crobuzon University, working under Vermishank, but left that job after finding that he was not any good at teaching. He works freelance assignments for the university to have access to its laboratories and purloining scientifc equipment whenever possible, while also making a living selling his services to people in need of his advanced science. He is described as "brilliant" and "undisciplined."

He has his own laboratory in Brock Marsh, where he shares a space with David Serachin and Lublamai Dadscatt. He often will fiercely study new topics that catch his curiosity, such as how the khepri's compound vision works, or how vodyanoi watercraeft works, before losing interest and moving onto new things. He has a passion for Unified Field Theory specifically attempting to tap Crisis Energy in an attempt to regain the power of flight for his client the de-winged Garuda Yaghagarek. His prototype Crisis Engine with help from the Construct Council and the Weaver resident in New Crobuzon is successfully used as an effective weapon killing several of the Slake Moths loose in the city.

Isaac is involved with Lin, a khepri artist, but keeps their relationship secret from his professional associates. He was a lover of Bellis Coldwine a major character in The Scar some years before the events of Perdido Street Station.

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