Introduction: Improved outcome has been shown in patients with synchronous oligometastatic (sOM) NSCLC when treated with radical intent. As a uniform definition of sOM NSCLC is lacking, we developed a definition and diagnostic criteria by a consensus process. Methods: A pan-European multidisciplinary consensus group was established. Consensus questions were built on the basis of current controversies, and definitions were extracted from a survey, cases and a systematic review. This statement was formulated during a consensus meeting. Results: It was determined that definition of sOM NSCLC is relevant when a radical treatment that may modify the disease course (leading to long-term disease control) is technically feasible for all tumor sites with acceptable toxicity. On the basis of the review, a maximum of five metastases and three organs was proposed. Mediastinal lymph node involvement was not counted as a metastatic site. Fludeoxyglucose F 18 positron emission tomography–computed tomography and brain imaging were considered mandatory. A dedicated liver magnetic resonance imaging scan was advised for a solitary liver metastasis, and thoracoscopy and biopsies of distant ipsilateral pleural sites were recommended for a solitary pleural metastasis. For mediastinal staging, fludeoxyglucose F 18 positron emission tomography–computed tomography was deemed the minimum requirement, with pathological confirmation recommended if this influences the treatment strategy. Biopsy of a solitary metastatic location was mandated unless the multidisciplinary team is of the opinion that the risks outweigh the benefits. Conclusion: A multidisciplinary consensus statement on the definition and staging of sOM NSCLC has been formulated. This statement will help to standardize inclusion criteria in future clinical trials.