The diamond knot (or knife lanyard knot) is a knot for forming a decorative loop on the end of a cord such as on a lanyard. A similar knot, also called the diamond knot, is a multistrand stopper knot, that is similar in appearance (although the footrope knot is really more similar, but it is simply an upside down diamond knot). To avoid confusion, it is advisable to call this knot the knife lanyard knot. This knot is a four strand diamond knot implemented in two strands. The knife lanyard knot is "tied alike" the Chinese button knot, "but they are worked differently." This knot is also used in Prayer ropes by Eastern Christians, who accredit the knot's creation to a legend relating to Saint Anthony the Great.

The sailor's knife lanyard knot, also called marling-spike lanyard knot, single-strand diamond knot, two-strand diamond knot, and Bosun's whistle knot.