This study provides a comprehensive quantitative analysis of the factors influencing English-speaking confidence among university students in Vietnam. In this context, English proficiency is a national strategic priority, yet speaking ability remains a significant challenge. Grounded in a socio-cognitive framework based on Bandura's self-efficacy theory, this research investigates a multi-factorial model encompassing six key predictors: Language Anxiety, Learner Motivation, Perceived Linguistic Competence, Teacher's Role, Peer Influence, and Exposure to English. A cross-sectional survey was administered to 361 undergraduate students from various universities across Vietnam. The data were analyzed using a three-stage process: Cronbach's Alpha for scale reliability, Exploratory Factor Analysis (EFA) to establish construct validity, and Ordinary Least Squares (OLS) multiple regression to test the predictive model. The results revealed that the proposed model significantly predicted learners' speaking confidence, explaining a substantial portion of the variance. Language Anxiety emerged as the most potent negative predictor, while a positive perception of the Teacher's Role and higher Perceived Linguistic Competence were the most potent positive predictors. These findings underscore that speaking confidence is not merely an innate personal trait but an emergent property shaped by a complex interplay of individual psychological states and the immediate pedagogical and social environment. The study concludes with concrete pedagogical implications for EFL teachers, curriculum designers, and policymakers in Vietnam, advocating for a holistic approach that prioritizes the creation of low-anxiety, supportive learning ecologies to foster the confidence necessary for effective oral communication.