This work proposes a circular-ring patch antenna using graphene as a patch material for breast tumor detection. Graphene's high dielectric conductivity enhances the antenna's bandwidth, making it suitable for medical applications. The antenna utilizes a Rogers substrate with overall dimensions of 30 × 30 × 0.7 mm. The ground plane is composed of copper, while the radiating patch is fabricated using graphene. The antenna is designed and simulated using CST Microwave Studio. Initially, the antenna is evaluated in free space, followed by tests on a normal breast phantom, a tumor-affected breast, and a cancerous breast using specific tissue properties to assess performance. In free space, the designed antenna exhibits an S1,1 parameter of −43.17 dB. Measurements within different breast tissue conditions show S1,1 value of −27.22 dB for normal breast tissue, −24.14 dB for a benign breast tumor, and −37.87 dB for a malignant breast tumor. Operating at 5.472, 7.416, 8.456, and 7.48 GHz, the antenna exhibits ultra-wideband (UWB) characteristics, ensuring high data transmission accuracy. The proposed antenna offers several advantages, including compact size, enhanced bandwidth, high sensitivity to tissue variations, low radiation exposure, and cost-effective implementation, making it a promising tool for early breast cancer screening, particularly in rural areas where access to advanced imaging technologies is limited.