This chapter conceptualizes ESG as a design variable in corporate finance that alters cash flows, risk profiles, and access to capital. Boards allocate resources to ESG initiatives, develop data infrastructure, and assign executive responsibility because environmental, social, and governance choices reshape operating variance, regulatory exposure, and growth opportunities. ESG strategy is defined as the systematic integration of E, S, and G factors into corporate purpose, capital budgeting, operating routines, and performance measurement. Materiality focuses attention on levers that affect unit economics or discount rates; governance distributes decision rights and accountability; data and assurance transform noisy operational signals into decision-useful metrics. Environmental programs create value through internal carbon pricing, long-term renewable contracts, process and logistics redesign, and lower-carbon asset selection. Social initiatives generate returns via human-capital productivity, workplace safety, supplier capability development, and customer retention. Governance enhances incentive alignment, strengthens controls and disclosure, and reduces agency costs. The chapter then examines a concrete governance lever: affiliated banker directors (ABDs) on corporate boards and their influence in mergers and acquisitions. Using variation in director–bank relationships and deal timing, the analysis finds that acquirers with ABDs experience higher announcement returns and stronger post-merger operating and market performance, with effects most pronounced under high information asymmetry and transaction complexity. Evidence supports three channels—information advantages, governance discipline, and a preference for diversifying deals that lower acquirer risk—demonstrating how board architecture can convert ESG-era constraints and opportunities into measurable value in one of corporate finance’s most consequential decisions.