This paper presents a methodology to assess the influence of geological uncertainty (stratigraphic uncertainty) on designing an offshore wind turbine foundation (OWTF). To consider the stratigraphic uncertainty, we create a synthetic stratigraphic model (SSM) and then sample multiple sets of boreholes to develop a series of stratigraphic models, each with a different degree of uncertainty (entropy). Using Markov random field (MRF) theory, these stratigraphic models were simulated, and their entropies were evaluated. The results indicate the entropies of the stratigraphic models decrease as the number of boreholes increases. The OWTF monopile is then designed based on these stratigraphic models with different entropy levels. Next, Monte Carlo simulation (MCS) is used to evaluate the failure probability of the design, considering uncertainties of the stratigraphic model and soil properties. Then, two monopile designs simulating piles located at different stratigraphic configurations are analyzed to assess the effects of stratigraphic uncertainty and strength parameter variability on their failure probabilities. Finally, insights gained regarding the effect of stratigraphic uncertainty on the OWTF monopile design are discussed.