Onions (Allium cepa L.) are widely cultivated and consumed vegetable crops around the world. Weed interference is the main limitation to onion production. Onions grow slowly, are short-statured, and are non-branching, which makes them difficult to compete with weeds. The aim of this study was to summarise the literature published between 2020 and 2025 that evaluated the effectiveness of different weed control methods used in onion cultivation using a systematic review following the PRISMA guidelines. Based on the results, pendimethalin and oxyfluorfen were the most used and most effective herbicides. Combining pre- and post-emergence treatments and spraying herbicide mixtures improved weed control efficiency compared with single treatments. Acetolactate synthase (ALS) inhibitors can adversely affect onions and reduce yield, making them unsuitable for use in onion production. Integrated weed management practises, such as combining herbicides with manual weeding and using plant-based extracts, offer a sustainable approach that can reduce reliance on chemicals. Mechanical weed management is not widely adopted in onion production because its application poses numerous challenges. The future direction of weed management should focus on technological advances in mechanical weed control and the development of bioherbicides to reduce reliance on synthetic herbicides.