A first measurement of deuteron production at the LHCb experiment is presented. The measurement is performed as a function of momentum, using proton-proton collision data from the 2018 data taking period, at a centre-of-mass energy √s =13 TeV. The simulation of deuteron production in proton-proton collisions, which is used extensively in the development of the measurement strategy, is described. The deuteron production cross-section measurement uses a neural network variable, ProbNNd, to discriminate between deuterons and other charged particles, in the momentum range 20 < p < 100 GeV/c, for pseudorapidities 1.89 < η < 4.89. Measurements of deuterons produced in high energy collisions provide important information for the calibration of models used in indirect dark matter searches. Some of these searches use antideuteron signals in cosmic-rays to look for evidence for dark matter annihilation. The measurement at LHCb is found not to be sensitive to a deuteron signal. The steps that should be followed to compute a deuteron production cross-section at LHCb are detailed.