Inclusion Criteria:  Confirmed diagnosis of CLL/SLL requiring therapy, per iwCLL 2018 criteria Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2 Adequate organ function Platelets greater than or equal to (≥)75 x 10⁹/liter (L) (≥50 × 10⁹/L for patients with evidence of bone marrow infiltrate), hemoglobin ≥8 grams/deciliter (g/dL), and absolute neutrophil count ≥0.75 x 10⁹/L Kidney function: Estimated creatinine clearance ≥40 milliliters per minute (mL/min)  Exclusion Criteria:  Known or suspected Richter's transformation at any time preceding enrollment Prior systemic therapy for CLL/SLL Presence of 17p deletion Central nervous system (CNS) involvement Active uncontrolled auto-immune cytopenia (e.g., autoimmune hemolytic anemia [AIHA], idiopathic thrombocytopenic purpura [ITP]) Significant cardiovascular disease Active hepatitis B or hepatitis C Active cytomegalovirus (CMV) infection Active uncontrolled systemic bacterial, viral, fungal, or parasitic infection Known human immunodeficiency virus (HIV) infection, regardless of cluster of differentiation 4 (CD4) count Concurrent use of investigational agent or anticancer therapy except hormonal therapy Patients requiring therapeutic anticoagulation with warfarin or another Vitamin K antagonist Vaccination with a live vaccine within 28 days prior to randomization  Patients with the following hypersensitivity:  Known hypersensitivity, including anaphylaxis, to any component or excipient of pirtobrutinib or bendamustine Prior significant hypersensitivity to rituximab