<p><span style=color: rgba(23 43 77 1)>This reprint of a Special Issue of&nbsp;</span><em style=color: rgba(23 43 77 1)>Mathematics</em><span style=color: rgba(23 43 77 1)>&nbsp;presents recent research on the theory and applications of optimization. The subjects that are addressed in the ten research papers cover a broad spectrum of optimization algorithms such as unconstrained optimization non-convex optimization multi-objective optimization graph theory or flow shop scheduling.</span></p>