The Downtown Eastside (DTES) is a neighbourhood in Vancouver, British Columbia, Canada. One of the city's oldest neighbourhoods, the DTES is the site of a complex set of social issues, including disproportionately high levels of drug use, homelessness, poverty, crime, mental illness and sex work.

Around the beginning of the 20th century, the DTES was Vancouver's political, cultural and retail centre. Over several decades, the city centre gradually shifted westwards, and the DTES became a poor neighbourhood, although relatively stable. In the 1980s, the area began a rapid decline due to several factors, including an influx of hard drugs, policies that pushed sex work and drug-related activity out of nearby areas, and the cessation of federal funding for social housing. By 1997, an epidemic of HIV infection and drug overdoses in the DTES led to the declaration of a public health emergency. As of 2018, critical issues include opioid overdoses, especially those involving the drug fentanyl; decrepit and squalid housing; a shortage of low-cost rental housing; and mental illness, which often co-occurs with addiction.

The population of the DTES is estimated to be around 7,000 people. Compared to the city, the neighbourhood is home to a significant Indigenous population, which reflects the ongoing impacts of colonial displacement and systemic inequities that have shaped the area’s demographics. Additionally, historical factors such as de-institutionalization, housing shortages, and limited access to mental health care have contributed to the concentration of poverty and substance use in the community. Residents experience Canada's highest rate of death from encounters with police, and there is mutual mistrust between police and many residents experiencing homelessness.

Since Vancouver's real-estate boom began in the early 21st century, the area has been increasingly experiencing gentrification. Some see gentrification as a force for revitalization, while others believe it has led to higher displacement and homelessness. Numerous efforts have been made to improve the DTES at an estimated cost of over $1.4 billion as of 2009. Services in the greater DTES area are estimated to cost $360 million per year. Commentators from across the political spectrum have said that little progress has been made in resolving the issues of the neighbourhood as a whole, although there are individual success stories. Proposals for addressing the issues of the area include increasing investment in social housing, increasing capacity for treating people with addictions and mental illness, making services more evenly distributed across the city and region instead of concentrated in the DTES, and improving coordination of services. However, little agreement exists between the municipal, provincial and federal governments regarding long-term plans for the area.

The term "Downtown Eastside" is most often used to refer to an area 10 to 50 blocks in size, a few blocks east of the city's Downtown central business district. The neighbourhood is centred around the intersection of Main Street and Hastings Street, where residents have gathered for over a hundred years to connect. This intersection is also the home of the Carnegie Community Centre. The area around Hastings and Main is where the neighbourhood's social issues are most visible, described in the Vancouver Sun in 2006 as "four blocks of hell."

Some indications of the borders of the DTES, which shift and are poorly defined, are as follows:

For some community planning and statistical purposes, the City of Vancouver uses the term "Downtown Eastside" to refer to a much larger area with considerable social and economic diversity, including Chinatown, Gastown, Strathcona, the Victory Square area, and the light industrial area to the north. This area, referred to in this article as the greater DTES area, is bordered by Richards Street to the west, Clark Drive to the east, Waterfront Road and Water Street to the north and various streets to the south including Malkin Avenue and Prior Street. The greater DTES area includes some popular tourist areas and nearly 20% of Vancouver's heritage buildings.

Strathcona in the 1890s included the entire DTES. By 1994 Strathcona's northern boundary was generally considered to be the alley between East Pender and East Hastings streets, though some place it at Railway Street, including DTES east of Gore Avenue.