<p>Optically addressable molecular spins are a promising qubit platform, combining the chemical versatility, atomistic tunability, nanoscale modularity, and structural diversity of molecules with the coherence, detection sensitivity, and remote connectivity of optically readable spins. Here, we review progress developing and deploying optically readable molecular spin qubits and the key opportunities they present, with a particular focus on quantum sensing. We survey key criteria for realizing optically addressable spin qubits in molecules; discuss existing and emerging platforms—spanning coordination complexes, organic molecules, and both ground and excited-state spins; and outline emerging applications, open challenges, and opportunities for combining the richness of chemical systems with the power of optically readable spin qubits.</p> Graphical abstract