Inclusion Criteria:  • Centrally reviewed CD20-positive follicular lymphoma grade 1/2 or 3a based on WHO classification (2008)  Untreated (radiation-, chemo- or immunotherapy) nodal follicular lymphoma (including involvement of Waldeyer´s ring) Age: ≥18 years ECOG: 0-2 Stage: clinical stage I or II (Ann Arbor classification) based on FDG-PET Staging Risk profile: Largest diameter of the lymphoma ≤ 7 cm (sectional images) Written informed consent and willingness to cooperate during the course of the trial Adequate bone marrow capacity: ANC ≥ 1.5 x 103/ml, thrombocytes ≥ 100000 x 10 3/ml, hemoglobin ≥ 10 g/dL Capability to understand the intention and the consequences of the clinical trial Adequate contraception for men and women of child-bearing age during therapy and 18 months thereafter  Exclusion Criteria:  Extra nodal manifestation of follicular lymphoma Secondary cancer in the patient's medical history (exclusion: basalioma, spinalioma, melanoma in situ, bladder cancer T1a, non-metastasized solid tumor in constant remission, which was diagnosed >3 years ago) Serious disease interfering with a regular therapy according to the study protocol, e.g: congenital or acquired immune-deficiency syndromes, active infections including viral hepatitis, uncontrolled concomitant diseases including significant cardiovascular or pulmonary disease Severe psychiatric disease Pregnancy / lactation Known hypersensitivity against Obinutuzumab or Rituximab drugs with similar chemical structure or any other additive of the pharmaceutical formula of the study drug Active hepatitis B infection (inactive hepatitis B infections require additional prophylactic anti-viral medication for 1 year (e.g. Lamivudin, Entecavir, Tenofovir) Participation in another interventional trial or follow-up period of a competing trial which can influence the results of this current trial Creatinine > 1.5 times the upper limit of normal (ULN) (unless creatinine clearance normal), or calculated creatinine clearance < 40 mL/min AST or ALT > 2.5 × ULN Total bilirubin ≥ 1.5 × ULN INR > 1.5 × ULN PTT or aPTT > 1.5 × the ULN