Victoria Oyerinde, ELP 2013, Nigeria   The greatest challenge to sustainable forest management (SFM) in Nigeria today is the increasing rate of illegal logging and encroachment. This is more rampant in the tropical rainforest ecosystem of Nigeria because of its richness in desirable tropical hardwood timber species and fertile land. Government policies, institutional support in forest management and enlightenment have not succeeded in curbing these problems. This is a great concern to all stakeholders and researchers in forestry. This situation has been presenting real challenges to professionals in forest management because it is now very difficult to determine the future of the tropical rainforest ecosystem in Nigeria. The development of forest resources management in Nigeria could be divided into three phases: the reservation phase between 1899 and 1930, the exploitation phase between 1930 and 1960 and the development phase from 1960 to date. Forest reserves are portions of forest estate constituted by law and gazetted by the State or Local Government. Entrance and activities such as logging, hunting, farming and collection of minor forest products in these reserves are controlled by the government. The available records in the Federal Department of Forestry show that Nigeria has a total of 1,160 constituted forest reserves covering a land area of about 1075 km2.  Rural development, encroachment, illegal logging, massive conversion to agriculture and large scale afforestation projects are some of the problems responsible for the disappearance of this natural forest ecosystem. Illegal logging and encroachment are the greatest threat to SFM today. The natural forest is now disappearing at an alarming rate of 3.5% (about 350,000 – 400, 000 ha) per annum. Illegal logging is the indiscriminate removal of logs from the forest without following the due process highlighted in government logging and harvesting policy. The illegally logged are usually converted into planks (flinches) at the site using a hand power-saw machine.  Illegally harvested timber constitutes more than 50% of the value of timber legally harvested in the country today. Encroachment is the unlawful acquiring of forest estates for settlement, farming and for any other illegal purposes. Causes of illegal felling in southwest Nigeria are the discretionary power of governments to de-reserve forests, lack of coherent and consistent forest policy, excessive bureaucracy in harvest management, poorly defined property rights, non-transparent allocation of concessions, corrupt government officials in charge of log control, over-capacity utilization in some timber industries, use of outdated management practices and inefficient log tracking system, “get-rich-quick” syndrome with most Nigerians and timber touts with political god fathers. Causes of encroachment include population growth, availability of fertile land in the forest ecosystem for farming, poverty, food insecurity, ignorance of these actions and lack of political will by the government to curb encroachment, especially by immigrants. Effects of Illegal logging and encroachment are environmental degradation and landscape deterioration, loss of plant and animal species (biodiversity) and their potential importance to man, loss of revenue to the government, global warming, loss of economic species, etc. The time is now to stem illegal logging and encroachment in Nigeria through capacity building, enforcement of laws and regulations and improved awareness of associated impacts.