Hydrogen peroxide (H₂O₂) is an environmentally benign oxidant because it generates water as the byproduct. It was reported in 2015 that the annual production of H₂O₂ is around 3–5 million tons, produced mainly by the anthraquinone process. However, the anthraquinone process suffers from the use of harmful organic solvents, limitations in centralized production, safety hazards in transportation, etc. To mitigate these issues and also to reduce the price, there is great scientific and industrial interest in the synthesis of H₂O₂ through alternate approaches such as photocatalytic and electrochemical routes. These techniques are preferable to the anthraquinone method, especially for water treatment by the advanced oxidation process that only requires about <1% wt/vol of peroxide dosage. This chapter focuses on recent studies that demonstrated photo- and electrochemical routes for H₂O₂ generation using various catalysts, and performance metrics like yield rates, apparent quantum efficiency, solar-to-chemical conversion efficiency (for phototcatalytic materials) and faradaic efficiency, and kinetic parameters (for electrocatalytic materials). Various reported methods for the quantification of H₂O₂ generated during photo/electrochemical processes are discussed. Reactor designs and future scope are also presented.