Bioelectronic medicine enables the treatment of a myriad of diseases that are often unresponsive to traditional therapeutics. While existing state-of-the-art devices such as the pacemaker or deep brain stimulator have been used for several decades in the clinic, the core technology has not changed since they were first invented. Major limitations for these technologies is that they have large device footprints which leads to more invasive surgeries, higher risks of site infections, post-operative complications, and the need for repeat surgeries. In this dissertation, I describe the advancement of next generation implantable bioelectronics, moving toward battery-free implants by leveraging a new branch of wireless power transfer technology. These battery-free bioelectronics take advantage of magnetoelectric materials to harvest electrical energy from an applied magnetic field, miniaturizing implants from the centimeter scale down to the millimeter regime. I demonstrate the first digitally programmable, wireless, endovascular peripheral nerve stimulator, called the MagnetoElectric BioImplanT (ME-BIT), which couples CMOS and ME materials. I further miniaturize the neural interface and develop a material based neural stimulator called the Magnetoelectric Nonlinear Metamaterial (MNM) which demonstrates the first nonlinear magnetoelectric coupling coefficient and we take advantage of this engineered metamaterial to directly stimulate excitable cells. Overall, magnetoelectrics hold significant promise for scalable next generation implantable bioelectronics for a variety of different applications.