  The Drinfeld double associated to the weak multiplier Hopf ($*$-) algebra
pairing $\left\langle A, B\right\rangle$ is constructed. We show that the
Drinfeld double is again a weak multiplier Hopf ($*$-) algebra. If $A$ and $B$
are algebraic quantum groupoids, then so does the double. We also prove the
correspondence between modules over the Drinfeld double and Yetter-Drinfeld
modules. Finally, we prove that the double is a quasitriangular weak multiplier
Hopf algebra.
