Abstract— In this paper, a novel flexible cloud shape loop antenna is designed and proposed for implantable applications at the Medical Device Radiocommunications Service (MedRadio 401-406 MHz) and Industrial, Scientific and Medical (ISM 433-434 MHz and 2.4-2.5 GHz) bands. The antenna has a small size; and it can be bent around small cylindrical implants that are 3.7 mm in radius and 10.6 mm in length. It is formed in the shape of a cloud to increase antenna radiation efficiency and gain by increasing its radiation resistance and near magnetic field in comparison with that for a typical elliptic cylindrical loop antenna. The radiation efficiency and gain of the proposed antenna are increased by 2.4 dB and 2.5 dBi, respectively, at 403 MHz in comparison with that for the elliptic cylindrical loop antenna. The antenna is also simulated in an anatomical arm model. The proposed antenna has many attractive features (small size, light weight and relatively good radiation efficiency and gain); and hence it could be a good candidate for implantable applications.