We report the presence of high significance diffuse radio emission from the Triangulum Australis cluster using observations made with the KAT-7 telescope and propose that this emission is a giant radio halo. We compare the radio power from this proposed halo with X-ray and SZ (Sunyaev–Zel'dovich) measurements and demonstrate that it is consistent with the established scaling relations for cluster haloes. By combining the X-ray and SZ data we calculate the ratio of non-thermal to thermal electron pressure within Triangulum Australis to be X = 0.658 ± 0.054. We use this ratio to constrain the maximum magnetic field strength within the halo region to be Bmax, halo = 33.08 μG and compare this with the minimum field strength from equipartition of Bmin, halo = 0.77(1 + k)2/7 μG to place limits on the range of allowed magnetic field strength within this cluster. We compare these values to those for more well-studied systems and discuss these results in the context of equipartition of non-thermal energy densities within clusters of galaxies.