Monopoles in string theory

A realization of En+1 monopoles in string theory is given. The NS five bran e stuck to an Orientifold eight plane is identified as the 't Hooft-Polyako v monopole. Correspondingly, the moduli space of many such NS branes is ide ntified with the moduli space of SU(2) monopoles. These monopoles transform in the spinor representation of an SO(2n) gauge group when n D8 branes are stacked upon the orientifold plane. This leads to a realization of En+1 mo nopole moduli spaces. Charge conservation leads to a dynamical effect which does not allow the NS branes to leave the orientifold plane. This suggests that the monopole moduli space is smooth for n < 8. Odd n > 8 obeys a simi lar condition. Using a chain of dualities, we also connect our system to an heterotic background with Kaluza-Klein monopoles.