The Relative Contribution of Ego Strength and Irrational Beliefs in Predicting Narcissistic Personality Disorder Among Teachers Abstract This research aimed to study the levels of narcissistic personality disorder, ego strength, and irrational beliefs among teachers, and to analyze the relationship between narcissistic personality disorder and both ego strength and irrational beliefs. Additionally, the research aimed to reveal the possibility of predicting narcissistic personality disorder based on ego strength and irrational beliefs, and to investigate the differences in these variables according to gender and experience level. The research sample consisted of (811) teachers from Al-Sharqia Governorate, aged between (28 & 47) years, with an average age of (37.24 ± 5.65) years. The research utilized the Narcissistic Personality Disorder Scale translated by the researcher, the Ego Strength Scale (prepared by the researcher), and the Irrational Beliefs Scale also translated by the researcher. The results showed that the level of narcissistic personality disorder among teachers was low in the overall score and some dimensions such as Contingent Self-Esteem and leadership, while it was moderate in dimensions like Grandiose Fantasy, Vanity, and Hiding Needs. The level of ego strength was moderate, tending towards high, while the level of irrational beliefs was moderate in the overall score and some dimensions like Self-downing and authoritarianism, and high in others like Low Frustration Tolerance and Demands for Justice. The results also indicated a negative correlation between narcissistic personality disorder and ego strength, and a positive correlation between narcissistic personality disorder and irrational beliefs. The dimension of self-related ego strength was found to be the most significant negative predictor of narcissistic personality disorder and its dimensions, while different dimensions of irrational beliefs predicted narcissistic personality disorder at varying levels. Irrational beliefs were found to have a greater contribution to the manifestation of narcissistic personality disorder compared to ego strength. Regarding gender differences, no statistically significant differences were found in the overall scores of the scales. However, there were differences between teachers with less than 10 years of experience and those with more than 10 years of experience. These differences favored teachers with less experience in terms of narcissistic personality disorder and irrational beliefs, while those with more experience showed higher ego strength. The findings were interpreted and discussed, along with recommendations and suggestions for future research. Keywords: Narcissistic Personality Disorder, Ego Strength, Irrational Beliefs, Teachers.