This study investigates how Vietnamese English-major students construct their Ideal L2 Self as English users. Semi-structured interviews with 34 university students were analyzed using grounded theory. The findings show that students’ Ideal L2 Self initially emerged from vivid, positive visions driven largely by external motives such as career aspirations. Over time, this vision was refined through influences from their educational and living contexts, including classroom learning and near-peer role models, which encouraged concrete action plans for English improvement. Social media and broader social experiences also shaped students’ imagined participation in global communities of practice, further sustaining their motivation. The analysis indicates that depending on the degree of internalization, external motives may evolve into either an Ideal L2 Self or an Ought-to L2 Self. This study contributes to understanding L2 motivation in Vietnam by highlighting how the Ideal L2 Self develops across contexts and supports long-term engagement in English learning.