A compact planar monopole antenna is proposed for ultra‐wideband applications. The antenna has a microstrip line feed and band‐rejected characteristics and consists of a ring patch and a partial ground plane with a defective ground structure of rectangular shape. An annular strip is etched above the radiating element and two slots, one C‐shaped and one arc‐shaped, are embedded in the radiating patch. The proposed antenna has been optimised using bio‐inspired algorithms such as the particle swarm optimisation and the firefly algorithm, based on a new software algorithm (Antenna Optimizer). Multi‐objective optimisation achieves rejection bands at 3.3–3.7 GHz for Worldwide Interoperability for Microwave Access, 5.15–5.825 GHz for the 802.11a wireless local area network system or HIPERLAN/2, and 7.25–7.745 GHz for C‐band satellite communication systems. Validated results show wideband performance from 2.7 to 10.6 GHz with S₁₁ < −10 dB. The antenna has compact dimensions of 28 × 30 mm². The radiation pattern is comparatively stable across the operating band with a relatively stable gain except in the notched bands.