INTRODUCTION: South African men are underrepresented in HIV testing and treatment services. Secondary distribution of oral HIV self-test (HIVST) kits by women living with HIV (WLHIV) to their male partners (i.e. index partner HIVST) may increase men's testing and treatment but has been understudied. METHODS: Between March and July 2021, we evaluated the effectiveness of index partner HIVST versus the standard of care (SOC) (invitations for men's facility-based testing) on men's testing in a 1:1 randomized control trial. Eligibility criteria included: WLHIV; ≥18 years of age; attending one of four high-density rural clinics; have a working cell phone; and self-reported having a primary male partner of unknown serostatus. The primary outcome was the proportion of WLHIV reporting that her partner tested for HIV within 3 months after enrolment. RESULTS: We enrolled 180 WLHIV and 176 completed an endline survey (mean age = 35 years, 15% pregnant, 47% unmarried or non-cohabiting). In the HIVST arm, 78% of male partners were reported to have tested for HIV versus 55% in SOC (RR = 1.41; 95% CI = 1.14-1.76). In the HIVST arm, nine men were reactive with HIVST (14% positivity), six were confirmed HIV positive with standard testing (67%) and all of those started antiretroviral therapy (ART), and four HIV-negative men started pre-exposure prophylaxis (PrEP) (5%). In SOC, six men were diagnosed with HIV (12% positivity), 100% started ART and seven HIV-negative men started PrEP (16%). One case of verbal intimate partner violence was reported in the HIVST arm. CONCLUSIONS: Secondary distribution of HIVST to partners of WLHIV was acceptable and effective for improving HIV testing among men in rural South Africa in our pilot study. Interventions are needed to link reactive HIVST users to confirmatory testing and ART.