What is the name of Burberry's signature plaid pattern?

Burberry’s signature plaid pattern is called the Burberry check.

The familiar check is a geometric design of intersecting stripes, traditionally associated with beige, black, white and red. Burberry used the pattern primarily as a lining in its trench coats before it became one of the most recognizable visual signatures in fashion.

The design emerged in the early 20th century and was in use by at least the 1920s. Its association with the trench coat helped connect the pattern to Burberry’s British outerwear heritage, while later use on scarves, bags and other accessories made it visible outside the coat itself.

“Burberry check” is the broad, canonical name used in general-reference sources. Individual variations and collections can have more specific names, including the Classic Check and Nova Check, but those are not the best general answer to this question. It is also sometimes loosely called tartan, although tartan is a broader category of woven patterns.