Critical thinking is, being utilized in the classroom and the curricula as a way to train decisive, open-minded individuals with fair judgmental qualities and speaking means deliver an idea, a topic, a presentation, and debate. This research aimed to find out the correlation between critical thinking and speaking ability. The research design of this study was correlation design using quantitative approach. The sample of this research was 30 students of fourth semester students in Mulawarman University in the academic year 2019/2020. The researcher chose the subject based on purposive sampling. The research instruments were critical thinking test which consisted of 40 questions that were distributed via google form and final assessment of speaking score from the lecturer. The result of the research showed that there is correlation between critical thinking and speaking ability. This was proven by the Sig -2 tailed is 0.0007 which is lower than the significant level 0.05 and person correlation is 485 which is higher than table correlation 361. It meant that the result of this research showed that critical thinking has correlation with speaking ability. It can be concluded that if students have a good critical thinking ability so they will have a better performance in speaking ability. Thus, there is correlation between critical thinking and speaking ability of the fourth semester students English Department in the academic year 2019/2020.