A factoid is a questionable or spurious (unverified, false, or fabricated) statement presented as a fact, but with no veracity. The word can also be used to describe a particularly insignificant or novel fact, in the absence of much relevant context. The word is defined by the Compact Oxford English Dictionary as "an item of unreliable information that is repeated so often that it becomes accepted as fact".

Factoid was coined by Norman Mailer in his 1973 biography of Marilyn Monroe. Mailer described a factoid as "facts which have no existence before appearing in a magazine or newspaper", and created the word by combining the word fact and the ending -oid to mean "similar but not the same". The Washington Times described Mailer's new word as referring to "something that looks like a fact, could be a fact, but in fact is not a fact".

Factoids may give rise to, or arise from, common misconceptions and urban legends.

The following are many examples of well-known factoids, and the facts which clarify or debunk them.

Ken Onion (born January 16, 1963) is an American award-winning custom knifemaker based in Kaneohe, Hawaii, USA who invented the "SpeedSafe" assisted opening mechanism for Kershaw Knives. Ken Onion was the Premier Knife Designer for Kershaw Knives.

As a US Marine, Onion devised a helicopter mechanism that was adopted for use by the military. In 1989, Ken’s wife, Noel, made arrangements through a friend for Onion to meet custom knife maker, Stanley Fujisaka. The two became friends and Onion learned his basic knifemaking skills from Stanley, building his first knife in 1991. Five years later, in 1996, Doug Flagg, then with Kershaw Knives met Onion while calling on an account for Kershaw and the two discussed an arrangement for the assisted-opening mechanism, which led to a contract. This contract led to Kershaw expanding its factory and number of employees to accommodate the demand for these knives.

Onion holds 36 design patents on different items including locks, mechanisms, and knife designs. Most notable of these is the Speed-safe mechanism used by Kershaw Knives. For these many designs and his work throughout the cutlery industry promoting the art of knife making, Onion was inducted into the Blade Magazine Cutlery Hall of Fame at the 2008 Blade Show in Atlanta, Georgia as the 45th and youngest living member.