Extinction has long been a central concern in biodiversity conservation. Today, de-extinction offers interesting possibilities of restoring charismatic species and ecosystem function, but also risks and costs. Most de-extinction depends on genetic engineering and synthetic biology. These technologies are also proposed for use in ‘gene tweaking’ in wild species to enhance their chance of survival. Within conservation, the resulting debates pit an optimistic world of high-tech ‘precision conservation’ against a more conventional vision of biodiversity conservation achieved primarily through protected areas. De-extinction is a fashionable idea that brings the complex debates about the ethics and wisdom of genetic engineering to a central position within conservation science