Bay K8644 is a chemical compound that functions as an L-type calcium channel agonist. Bay K8644 is used primarily as a biochemical research tool for this effect. It is a structural analog of nifedipine with positive inotropic activity, and as an aromatic it is highly lipid soluble.

Bay K8644 targets L-type voltage-gated calcium channels. It is the first positive inotropic agent shown to act specifically and directly on calcium channels.