Graham Thalben Ball, professionally known as Johnny Ball (born 23 May 1938), is an English television personality, children's television presenter, writer and populariser of mathematics. Ball regularly appeared on British television for several decades, predominantly on the BBC, from 1967, featuring in or presenting programmes such as Play School, Think of a Number, Think Again, Think It ... Do It, Think...This Way and Johnny Ball Reveals All. He has also published a number of non-fiction books.

Ball was born in Bristol and attended Kingswood Primary School on the eastern edge of the city (now outside Bristol). Later in his childhood the family moved to Bolton, then part of Lancashire, where he attended Bolton County Grammar School. He left formal education with two O-Levels, one in mathematics and one in geography. He was called up for national service and spent three years in the Royal Air Force. He was posted to Wales as a radar operator and was later sent to Germany to monitor the Hamburg-Berlin air corridor.

Ball began his entertainment career by working as a Butlin's Redcoat, and was an entertainer in northern clubs and cabaret. He was nicknamed Johnny after John Ball, who played for Bolton Wanderers from 1950 to 1958 and the name stuck.

Ball was one of the hosts of pre-school programme Play School beginning in 1967 and continuing throughout the 1970s and beyond. He was also a regular fixture on children's television from the mid 1970s and throughout the 1980s, presenting several series of science and technology programmes intended for children, including Think of a Number; Think Again; Think Backwards; Think...This Way and Johnny Ball Reveals All. As well as appearing on screen Ball wrote jokes for some shows including Crackerjack. All of these shows (except the ITV programme ...Reveals All) appeared on the BBC. Ball's shows were known for presenting scientific and technological principles in an entertaining and accessible way for young people.

In 2003, Ball appeared on The Terry and Gaby Show in which he answered viewers' questions. In July 2004, he was named in the Radio Times list of the top 40 most eccentric TV presenters of all time. In July 2012, he presented a Horizon special on ageing on BBC Four. He has starred in ITV and Channel 4 television adverts as well as radio adverts for the Yorkshire-based firm Help-Link.

In 2012, Ball took part in the Strictly Come Dancing television show, where he was paired with Aliona Vilani. A training accident in the three-week interval resulted in torn ligaments for Vilani, causing her to retire temporarily from the show. She was replaced by Iveta Lukošiūtė who, with Ball, was eliminated in the first week. Vilani returned in the final group dance alongside Ball. In an interview in October 2017, Ball said that Vilani faked the injury, with Vilani denying the allegation and saying she would take legal advice over Ball's comments. There are no reports that she subsequently took any form of legal action.^{[citation needed]}

Ball married Julia (née Anderson) in 1969. The marriage produced one child, television and radio presenter Zoe Ball, before their divorce in 1972.

Ball married Diane (née Hicks) in 1975. The couple live in Buckinghamshire.