Religious institutions and beliefs play important and varying roles in the development work. Purposeful engagement between development and religious actors has increased in recent decades, reflecting recognition that religion plays both positive and less positive roles. Religious engagement touches every facet of development work, from economic policies to health, education, and water, to protection of vulnerable communities. Evidence produced by various disciplines (economics, anthropology, political science, and psychology), and by operational entities deepens appreciation for religion’s distinctive roles. With extraordinary diversity among religious communities, roles and caliber of engagement vary widely, calling for contextual understandings at country or community level. Among priority topics for attention are gender equality, governance, and inequality. Religious roles need to be appreciated as complex, fundamental, and integral parts of landscapes within which development transpires. This chapter by Katherine Marshall was published in the Handbook on Religion and International Affairs, part of the Elgar Handbooks in Political Science series.