An electrosurgical instrument 35 having: a distal part comprising an instrument tip 37 for applying radiofrequency and/or microwave frequency energy to tissue, the instrument tip comprising first and second conductive elements (23, 27, figure 2A); a coaxial feed cable 39 with its inner conductor electrically connected to the first conductive element and its outer conductor electrically connected to the second conductive element through a rotatable connection that allows rotation of the distal part relative to the coaxial feed cable; and the instrument comprises an actuator, optionally a rod 49, for rotating the distal part in a first rotational direction relative to the feed cable. A spring 43 may bias the tip against rotation and a stop element may prevent rotation in a second, opposite direction. Also disclosed is an RF/MW electrosurgical instrument having a plurality of bearings (103, figure 12) positioned between the coaxial feed cable (99) and a surrounding housing or sheath (101) for enabling relative rotation. The bearings may be ball bearings or brush bearings.