Onion (AIlium cepa) is considered as the most vital crop of Allium group. It is one of the most useful vegetable crops because it forms an indispensable part of many diets. It is considered as the friendly crop to both old and young. Onion is useful for its bulbs possessing characteristics flavour, odour and pungency. Onion has the ability to cure many iliments including stopping of bleeding, inhibiting human stomach cancer, curing sleeping disorders, etc. Onion is considered as a highly export vegetable crop and earns a reasonable foreign exchange for the country. Weeds which are worthless species of plants to the small-scale farmers are troublesome in onion production as they interfere with production of crop and add to the cost of the cultural practices involved in onion production especially in weeding. The lowering of onion yield has a direct relationship with weed competition. Weeds also reduce the quality of crop yield. Onion shows higher susceptibility to weed interference when compared with other vegetable crops owing to its characteristics like shallow roots, lack of dense foliage, slow growth, etc. The effective weed control in onion production include preventive, integrated, biological, mechanical methods, etc. The use of herbicides is also of great importance in weed control in onion production. Spraying of pre-emergence herbicides keeps the onion in weed free condition during the early stages and the use of post emergence herbicides are useful to reduce damage to the onion bulb, weed competition and cost of weeding.