Theydon Bois is a village and civil parish in the Epping Forest district of Essex, England. It is 1.4 miles (2.2 km) south of Epping, 0.85 miles (1.3 km) northeast of Loughton and 6 miles (9.6 km) south of Harlow. The population was 4,062 as at the 2011 Census.

Theydon Bois is inside the M25 motorway near to its junction with the M11 motorway. It is served by Theydon Bois tube station on the Central line and has one primary school, Theydon Bois County Primary School. It lies on the edge of Epping Forest. It also has the Theydon Bois Interchange.

A notable characteristic of the village is its almost complete absence of street lighting. Villagers have consistently voted against the installation of such lighting for decades, fearing that it would damage the traditional village ambience and require a rise in council tax. Only the approach to the tube station features a small number of lampposts.

What is widely regarded as Theydon Bois' most iconic landmark is the 'Avenue of Trees' which lines Loughton Lane, one of its main roads. The oak trees were planted in the 1830s to, reputedly, celebrate the accession of Queen Victoria to the throne. Chairwoman of the City of London's Epping Forest Committee, said, "The Theydon avenue [has been] identified as the highest priority among the many other avenues of trees that the City of London currently looks after."

A recent survey commissioned by the City of London, the responsible authority for the Green, found that four of the trees were required to be felled and others should be monitored.

Although felling was accepted as necessary, there was local concern about the visual impact that this would have on the village. A new line of trees, therefore, was planted in late 2010, set back from the current row. The semi-mature replacements will eventually dominate the site. The TBPC chairman, Robert Glozier, said, "The Avenue of Trees is an intrinsic part of the village. It has to be preserved not just for the short term but also the long term and the best way to do this is to have a parallel Avenue of Trees to take over".

Some of the new trees have been sponsored as memorials, and details of these will be printed on an information board near the avenue.