The Antiretroviral Therapy as Long Acting Suppression (ATLAS) study is being conducted to establish if human immunodeficiency virus type-1 (HIV-1) infected adult participants with current viral suppression on a regimen with 2 nucleoside reverse transcriptase inhibitors (NRTIs) plus a third agent, remain suppressed upon switching to a two-drug intramuscular (IM) long-acting (LA) regimen of cabotegravir (CAB) and rilpivirine (RPV). This is a Phase 3, multi-phase, randomized, open label, active-controlled, multicenter, parallel-group, non-inferiority study in HIV-1, antiretroviral therapy (ART)-adult participants who are stably suppressed on a current antiretroviral (ARV) regimen. This study is designed to demonstrate the non-inferior antiviral activity of switching to a two drug CAB LA 400 mg + RPV LA 600 mg regimen every 4 weeks (Q4W: monthly) compared with maintenance of current ARV regimen containing 2 NRTIs plus an INI, NNRTI, or a PI. Eligible participants will be randomized (1:1) into the Maintenance Phase at Day 1 to either continue current ART or switch to initiate oral therapy with CAB 30 mg + RPV 25 mg once daily for 4 Weeks followed by Q4 weekly (monthly) CAB LA + RPV LA injections. Following the Maintenance phase at Week 52, participants who were randomized to continue their current ART regimen will be given an option to switch to CAB LA + RPV LA injections. Those participants would transition to LA dosing, beginning with 4 weeks oral CAB + RPV therapy at Week 52, and receive the first IM CAB LA + RPV LA injections at Week 56.