Inclusion Criteria:

          -  Men and women ≥ 18 years of age.

          -  Pathologically confirmed MCL.

          -  Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 2.

          -  Agreement to use highly effective forms of contraception during the study and for 2
             days after the last dose of acalabrutinib, 30 days after the last dose of venetoclax,
             or 12 months after the last dose of rituximab, whichever is longest.

          -  Treatment Naive MCL patients requiring treatment with no exposure to prior therapies.

        Exclusion Criteria:

          -  Significant cardiovascular disease such as uncontrolled or untreated symptomatic
             arrhythmias, congestive heart failure, or myocardial infarction within 6 months of
             screening, or any Class 3 or 4 cardiac disease as defined by the New York Heart
             Association Functional Classification.Exception: Subjects with controlled,
             asymptomatic atrial fibrillation during screening are allowed to enroll on study

          -  Malabsorption syndrome, disease significantly affecting gastrointestinal function,
             resection of the stomach, extensive small bowel resection that is likely to affect
             absorption, symptomatic inflammatory bowel disease, partial or complete bowel
             obstruction, or gastric restrictions and bariatric surgery, such as gastric bypass

          -  Uncontrolled active systemic fungal, bacterial, viral, or other infection (defined as
             exhibiting ongoing signs/symptoms related to the infection and without improvement,
             despite appropriate antibiotics or other treatment), or intravenous anti-infective
             treatment within 2 weeks before first dose of study drug

          -  Breastfeeding or pregnant

          -  Concurrent participation in another therapeutic clinical trial.