This paper forecasts the United States’ military spending in absolute terms and as a percentage of Gross Domestic Product (GDP) based on autoregressive integrated moving average (ARIMA) models. Military spending data for the period 1949-2016 collected by the Stockholm International Peace Research Institute (SIPRI) is used. For each forecast period, the ARIMA model outputs the forecast value, a standard error estimate for the forecast value, and the lower and upper limits for a 95% prediction interval. Results obtained reveal that the ARIMA model has a strong potential for short-term prediction.