This chapter positions prompt engineering as an emerging professional discipline shaped by expanding technical, ethical, and institutional responsibilities. It traces the evolution of prompting from informal experimentation to a structured practice embedded in real-world systems across education, healthcare, governance, and industry. The discussion emphasizes the shift from isolated interaction to infrastructural design, where prompts influence large-scale user experiences and decision-making processes. It introduces core literacies, cognitive, ethical, communicative, and systemic, as foundational competencies for professional practice. The chapter broadens the definition of a prompt engineer to include all individuals whose prompt design affects others within applied contexts. It examines the growing prompt ecosystem, highlighting the role of interdisciplinary collaboration and domain-specific knowledge. Key risks, including representational, epistemic, and institutional harms, are analyzed alongside emerging regulatory frameworks and governance mechanisms. The chapter proposes a professional code of practice to guide responsible, transparent, and human-centered prompt design. A competency map outlines developmental pathways from foundational literacy to system-level design and governance. Ultimately, the chapter frames prompt engineering as a form of public infrastructure, requiring sustained ethical commitment, institutional accountability, and alignment with human dignity and social trust.