The halting problem is a very famous example from computability theory of a problem that is undecidable. It is often said that the proof of its undecidability was given by Alan Turing, indeed wikipedia repeatedly says so.
However, Turing's paper "On Computable Numbers, with an Application to the Entscheidungsproblem" does not deal with the halting problem at all. As Charles Petzold writes in "The Annotated Turing", page 234:
The halting problem has subsequently become closely identified with Turing Machines, but the concept is foreign to Turing's original paper.
The problems that Turing's paper does show are undecidable are the problem of deciding whether a Turing machine is circle-free (which is not the same as halting, since both circle-free and circular machines can keep printing forever), that of deciding whether a machine ever prints some specific symbol, and that of the Entscheidungsproblem. Of course, the problem of deciding whether a Turing machine is circle-free is very close to the halting problem, but it is nonetheless not the halting problem. I am aware that the term "halting problem" was coined by Martin Davis in 1958.
My question is, if Alan Turing never discussed the halting problem, why do so many sources attribute it to him?