We conducted a paired correspondence experiment in Buenos Aires, Argentina, to measure the extent of labor market discrimination in hiring against slum dwellers. We sent 4,290 online pairs of fictitious job applications of otherwise observationally equivalent individuals who differed in a single attribute: place of residence, either a slum or not. We found that job applicants living in slums received nearly 28 percent fewer callbacks than other applicants. We observe discrimination across jobs that require a university degree, with discrimination being concentrated in administrative and software-related occupations. We observed discrimination against both men and women living in slums. Discrimination also varied by occupation. Discrimination against slum dwellers is an invisible barrier that affects their employment probability, ultimately reducing their likelihood of graduating from poverty.