This chapter examines availability – the likelihood that a consumer finds the desired item across channels – as a decisive driver of satisfaction and conversion. Using Nike as illustration, it distinguishes physical availability, informational transparency, and network coverage. Mismatches between inventory and demand lead to lost sales, substitutions, or channel leakage, especially in omnichannel environments. The chapter reviews preventive tools such as forecasting, safety stock, and allocation optimization, alongside reactive measures like rebalancing and rerouting. Data-rich signals and machine-learning forecasts now enable more precise, real-time availability management. Availability becomes a service promise requiring calibrated trade-offs among working capital, risk, and customer experience.