We present a genome assembly from an individual male Machimus rusticus (Downland Robberfly; Arthropoda; Insecta; Diptera; Asilidae). The genome sequence spans 279.70 megabases. Most of the assembly is scaffolded into 8 chromosomal pseudomolecules, including the X and Y sex chromosomes. The mitochondrial genome has also been assembled and is 16.38 kilobases in length. Gene annotation of this assembly on Ensembl identified 11,510 protein-coding genes.