This paper reports the observation of superconductivity in monolayer NbSe$_2$ with an in-plane upper critical field that is over six times the Pauli paramagnetic limit, as determined by magneto-transport measurements. The study highlights the role of spin-momentum locking and strong intrinsic spin-orbit interactions in non-centrosymmetric NbSe$_2$ monolayers, where the electronic spin is locked to the out-of-plane direction. This effect is attributed to the competing Zeeman effect and large spin-orbit interactions, leading to unconventional Ising pairing. The results provide strong evidence for spin-momentum locking-protected superconductivity and open new avenues for studying non-centrosymmetric superconductivity with unique spin and valley degrees of freedom in the exact two-dimensional limit. The experimental findings are supported by theoretical analysis and ab initio calculations, demonstrating the importance of spin-orbit interactions in enhancing the upper critical field in monolayer NbSe$_2$.This paper reports the observation of superconductivity in monolayer NbSe$_2$ with an in-plane upper critical field that is over six times the Pauli paramagnetic limit, as determined by magneto-transport measurements. The study highlights the role of spin-momentum locking and strong intrinsic spin-orbit interactions in non-centrosymmetric NbSe$_2$ monolayers, where the electronic spin is locked to the out-of-plane direction. This effect is attributed to the competing Zeeman effect and large spin-orbit interactions, leading to unconventional Ising pairing. The results provide strong evidence for spin-momentum locking-protected superconductivity and open new avenues for studying non-centrosymmetric superconductivity with unique spin and valley degrees of freedom in the exact two-dimensional limit. The experimental findings are supported by theoretical analysis and ab initio calculations, demonstrating the importance of spin-orbit interactions in enhancing the upper critical field in monolayer NbSe$_2$.