Structural variation has played an important role in the evolutionary restructuring of human and great ape genomes. We generated approximately 10-fold genomic sequence coverage from a western lowland gorilla and integrated these data into a physical and cytogenetic framework to develop a comprehensive view of structural variation. We discovered and validated over 7,665 structural changes within the gorilla lineage, including sequence resolution of inversions, deletions, duplications and mobile element insertions. A comparison with human and other ape genomes shows that the gorilla genome has been subjected to the highest rate of segmental duplication. We show that both the gorilla and chimpanzee genomes have experienced independent yet parallel patterns of structural mutation that have not occurred in humans, including the formation of subtelomeric heterochromatic caps, the hyperexpansion of segmental duplications, and bursts of retroviral integrations. Our analysis suggests that the chimpanzee and gorilla genomes are structurally more derived than either orangutan or human genomes.