Delafossites are a class of metal oxides with the chemical formula ABO2 where A is a monovalent cation, and B is a trivalent cation. These materials have been notable for their high modularity, potential as transparent conducting oxides (TCOs), and potential as quantum spin liquids. Much work has been done to tune their electrical and optical properties. Copper delafossites have had excellent work examining how their structures evolve with pressure. Previous studies of copper delafossites have found polymorphs stable exclusively at pressure. Chapter 1 will introduce delafossites and why they interest the broader materials science community. It will also discuss their various applications, introduce the diamond anvil cell, and special considerations for studying materials under extreme pressure. Chapter 2 contains all of the experimental techniques, data, and data analysis of the first study of silver ferrite delafossite, AgFeO2, at pressure. This chapter is presented as it appears in Inorganic Chemistry. The text and images are unaltered from their published version but are formatted to be consistent with the rest of the thesis. This work includes Raman spectroscopy, infrared spectroscopy, phonon calculations, Xray diffraction, and nuclear resonant forward scattering experiments. Chapter 2 also reports a novel synthesis of AgFeO2 that yielded single crystals of a size never made before, allowing for high-quality data collection. These data allowed us to identify two new high-pressure polymorphs of AgFeO2 that are stable above ∼6GPa and ∼14GPa. We have assigned the first high-pressure structure as a monoclinic C2/c structure. Both the spin state and valence state of AgFeO2 are stable at the Fe3+ site up to 15.3(5)GPa. Chapter 3 contains experimental work on silver aluminum delafossite, AgAlO2. This work includes Raman spectroscopy, infrared spectroscopy, and X-ray diffraction data. This chapter provides a road map on the steps to improve the synthesis of AgAlO2 and collect high-quality data. A pressure-induced phase transition is reported above ∼19GPa. Chapter 4 provides a review of delafossites studied under pressure. The field’s limitations will also be reviewed. This chapter investigates new insights into the effect of the A site cation on pressure-induced phase transitions. Given the novel work presented in Chapter 2 and Chapter 3, we are in a unique position to compare the behavior of silver delafossites under pressure and copper delafossites under pressure. Additionally, the trends in silver delafossite phase transitions under pressure are explored. Chapter 5 summarizes the work presented in this dissertation and reevaluates the phase space of delafossites. Improvements in high-pressure single-crystal X-ray diffraction are highlighted. Future work and applications are also discussed, such as the synthesis of gold delafossites and potential computational studies to characterize high-pressure polymorphs.