This paper focuses on two types of boast words as they are used in Beowulf. The first type to be considered is the act of speaking we commonly associate with bragging, while the second, more important kind of boast, functions as a promise that the speaker will perform specific acts of courage. Close examination of Beowulfs speeches in their narrative contexts shows that type one boasts, as they are defined here, help to establish Beowulfs credibility as a man who can be trusted to do what he says he will do, while type two boasts show the degree to which he commits himself to follow through on his promises. Attention is also given to the boast words Wiglaf utters as he comes to the aid of his king, and to words spoken by J.R.R. Tolkiens Lord of the Rings heroes that also function, in their much later contexts, as type two, heroic promise boasts.