In the present research, we proposed a systematic approach to disentangling the shared and unique variance explained by achievement goals, reasons for goal pursuit, and specific goal-reason combinations (i.e., achievement goal complexes). Four studies using this approach (involving nearly 1,800 participants) led to 3 basic sets of findings. First, when testing goals and reasons separately, mastery (-approach) goals and autonomous reasons explained variance in beneficial experiential (interest, satisfaction, positive emotion) and self-regulated learning (deep learning, help-seeking, challenging tasks, persistence) outcomes. Second, when testing goals and reasons simultaneously, mastery goals and autonomous reasons explained independent variance in most of the outcomes, with the predictive strength of each being diminished. Third, when testing goals, reasons, and goal complexes together, the autonomous mastery goal complex explained incremental variance in most of the outcomes, with the predictive strength of both mastery goals and autonomous reasons being diminished. Comparable results were observed for performance (-approach) goals, the autonomous performance goal complex, and performance goal-relevant outcomes. These findings suggest that achievement goals and reasons are both distinct and overlapping constructs, and that neither unilaterally eliminates the influence of the other. Integrating achievement goals and reasons offers the most promising avenue for a full account of competence motivation. Educational Impact and Implications Statement The present research seeks to disentangle the influence of "what" individuals want to achieve (type of goals), "why" they want to achieve (type of reasons), and specific "what" and "why" combinations (type of goal-reason combinations). In four studies, we showed that mastery goals (striving for task mastery), autonomous reasons (striving because it is stimulating and valued), and a specific mastery goal-autonomous reason combination (striving for task mastery because it is stimulating and valued) all made separate positive contributions to beneficial achievement-relevant outcomes (e.g., interest, positive emotion, deep learning). Comparable results were observed for performance goals (striving to outperform others) and a specific performance goal-autonomous reason combination (striving to outperform others because it is stimulating and valuable). The present findings indicate that both type of goals and type of reasons are important for a full understanding of achievement motivation.