A do-while loop is a control structure used in programming that allows a block of code to be executed at least once before checking a condition. This means that the code inside the loop will run first, and then the condition is evaluated. If the condition is true, the loop will continue to execute; if false, it will stop. The syntax of a do-while loop typically includes the keyword do, followed by a block of code in curly braces, and then the while keyword with a condition in parentheses. This structure ensures that the loop's body is executed before any condition is tested, making it useful for scenarios where at least one execution is necessary.