Biomass is a widely used renewable energy source, whose uptake is growing due to concerns about the impact of anthropogenic fossil fuel combustion on climate change. Waste biomass-derived fuels and chemicals offer a partial solution to reducing global reliance on fossil fuels in pursuit of Net Zero 2050 CO2emissions, in concert with environmental, health, and economic benefits. Biorefineries aim to convert biomass resources such as forestry and agricultural waste into diverse product streams, akin to the processing of nonrenewable fossil fuels by petrochemical refineries. However, realizing this ambition requires design of hydrothermally stable catalysts with tunable redox properties and acid-base character to promote molecular deoxygenation or the interconversion of oxygen functionalities. Perovskite oxides of general formula ABO3(where A = rare or alkaline earth cations and B = transition metal cations) exhibit structural flexibility and diverse surface chemistry; ∼90% of all metals can be introduced to perovskite oxides. Here, we review recent developments in the use of perovskite oxide catalysts for biomass valorization, focusing on structure-reactivity relationships in hydroprocessing, oxidation, steam reforming, and acid-base reactions. Prospects and challenges for the broader application of perovskite oxide catalysts to biomass valorization are also highlighted. © 2023 American Chemical Society. All rights reserved.