How Many Descendants Did Oliver Cromwell Have?

Not exactly known, but probably dozens if not more, are still living.

Oliver Cromwell and his wife Elizabeth had six children who survived in to adulthood.  Three of these did not have great-grandchildren of their own, but the other three (from Henry, Bridget and Frances) established lines that extended down until at least Victorian times.

You can look at the Cromwell Association website, if you think you might be one of his descendants.

Other family names that married into the Cromwell line before Oliver Cromwell's birth were Williams, Tudor and Steward (read more here).  By the usual marriage rules, Cromwell's own family name should have been Williams, but for political reasons and to advance their own self-interests, the surname Cromwell, with a more illustrious history, was adopted by his male ancestors.

One of Cromwell's descendants is Katherine Worsley, who in 1961 married Prince Edward, The Duke of Kent (member of the Royal Family and cousin of QE II).