Gender and inclusion in second language (L2) teaching practices constitute a critical but persistently undertheorised nexus at the intersection of applied linguistics, feminist pedagogy, and educational equity. This paper presents a comprehensive, theoretically grounded conceptual synthesis examining how gender operates as a structuring force in L2 classrooms, shaping learner motivation, participation patterns, identity formation, material representations, and teacher practice, with specific attention to the Nigerian and broader Sub-Saharan African educational context. Drawing on Feminist Pedagogy, Social Constructivist Theory, Butler's theory of Gender Performativity, Crenshaw's Intersectionality Framework, and Dörnyei's L2 Motivational Self System, the paper advances a five-domain framework for understanding gender-inclusive L2 teaching: (1) gendered learner motivation and L2 identity; (2) classroom interaction and participatory equity; (3) gender representation in L2 teaching materials; (4) teacher practices, positionality, and professional development; and (5) institutional and policy dimensions of gender-inclusive L2 education. For each domain, the paper examines empirical evidence, identifies critical research gaps, and proposes evidence-based strategies for gender-transformative L2 pedagogy. The paper argues that gender inclusivity in L2 teaching is not a peripheral equity concern but a pedagogical and social justice imperative with measurable consequences for learner outcomes, teacher effectiveness, and the broader educational project of equipping diverse populations with the communicative and critical competencies necessary for full social participation.