Overconfidence bias and the Dunning-Kruger effect are quite similar in that they both refer to unwarranted confidence. However, there is a difference between them:
Overconfidence bias refers to people’s tendency to wrongly overestimate their knowledge or ability in a specific area, sometimes in comparison to others.
On the other hand, the Dunning-Kruger effect specifically refers to how people who lack experience, ability, or expertise in a certain domain of knowledge or in a given task tend to overestimate themselves.
In other words, overconfidence bias denotes a more universal tendency while the Dunning-Kruger effect denotes the overconfidence of those who are unskilled at a particular task.