Ron already mentioned this in the comments but let me try to offer a little more explanation.
SD-WAN, from a vendor perspective, is offered as a solution which involve a set of technologies designed to simplify deployment and traffic management over WAN. It's a child of the "SDN" umbrella, and basically means you would have software doing a lot of automation for you for device provisioning(instead of a NE popping into the hardware and configuring the CLI) and you(the user) can manage a lot of things(mostly) from a dashboard. Capabilities offered as part of solution vary by vendors.
Viptella's vEdge, CISCO's IWAN, VMWare's VeloCloud are some examples of this.
MPLS VPN, on the other hand, is a VPN created over a MPLS underlay. This VPN can allow you to route packets ( L3 VPN ) or switch frames ( pseudowire, VPLS ).