No, not all DVDs include surround sound. A DVD can contain audio in various formats, ranging from simple stereo (two channels) to full 5.1 surround sound or even 7.1 surround sound. The audio format depends on what the content creator decided to include when producing the disc.
Most mainstream movies on DVD typically do include surround sound options, often in Dolby Digital 5.1 format, because cinematic experiences benefit from directional audio. However, many DVDs—particularly older releases, budget releases, or non-fiction content like documentaries and TV shows—may only have stereo audio tracks. Some DVDs offer multiple audio options, allowing viewers to choose between stereo and surround sound depending on their home audio setup.
To find out what audio format a specific DVD contains, you can check the packaging information, which typically lists the audio specifications. When playing a DVD, your player and receiver will automatically detect and output whichever audio format is selected. If you only have stereo speakers or choose a stereo-only soundtrack, you'll hear standard two-channel audio even if surround sound options are available on the disc.