The most commonly cited answer is Sir Isaac Newton , who was born on Christmas Day according to the calendar used in England at the time.

Newton’s Christmas birthday

  • Isaac Newton was born on 25 December 1642 in England under the old Julian calendar, which his family and country used at the time.
  • When converted to the modern Gregorian calendar, this date corresponds to 4 January 1643, but Newton is still widely described as a “Christmas Day” baby in historical anecdotes and quizzes.

Why Newton is the usual quiz answer

  • Newton is often called the greatest scientist of all time for his work on the laws of motion, universal gravitation, optics, and calculus, so his unusual Christmas birth date is a popular trivia fact.
  • Several articles and history pieces specifically highlight him as “the most famous scientist born on Christmas Day,” which is why quizzes and forum discussions almost always expect “Isaac Newton” as the answer.

Other scientists with Christmas birthdays

  • Lists of “scientists born on Christmas Day” also mention figures such as chemist William Gregor (discoverer of titanium), Nobel Prize–winning chemist Adolf Windaus, and physicist Gerhard Herzberg.
  • Despite these other names, none are as globally well known as Newton, so when someone asks “which famous scientist was born on Christmas Day,” the intended answer is Isaac Newton.

TL;DR: The famous scientist almost always meant by this question is Sir Isaac Newton.

Information gathered from public forums or data available on the internet and portrayed here.