A light-hole exciton is a quasiparticle formed from a single electron bound to a single light hole. This type of fundamental
excitation, if confined inside a semiconductor quantum dot, could be advantageous in quantum information science and
technology. However, it has been difficult to access it so far, because confinement and strain in conventional quantum dots
favour a ground-state single-particle hole with a predominantly heavy-hole character. Here we demonstrate the creation of a
light-hole exciton ground state by applying elastic stress to an initially unstrained quantum dot. Its signature is clearly distinct
from that of the well-known heavy-hole exciton and consists of three orthogonally polarized bright optical transitions and a
fine-structure splitting of hundreds of microelectronvolts between in-plane and out-of-plane components. This work paves the
way for the exploration of the fundamental properties and of the potential relevance of three-dimensionally confined light-hole
states in quantum technologies.