List of Maryland state highways

Standard route signs in Maryland
Highway names
Interstates:	Interstate X (I-X)
US Routes:	U.S. Route X (US X)
State:	Maryland Route X (MD X)
System links
Maryland highway system Interstate • US • State • Minor • Former • Turnpikes

Maryland Route 355 in Rockville
	List of Maryland state highways (2-199)
	List of Maryland state highways (200-399)
	List of Maryland state highways (400-599)
	List of Maryland state highways (600-799)
	List of Maryland state highways (800-999)

On the right are segments of the list of Maryland state highways, split into groups of 200. Maryland state numbered highways are typically referenced as Maryland Route X. The highways are most often abbreviated as MD X, with MD Route X and Route X being used less frequently. The longest state highway in Maryland is Maryland Route 2 (MD 2) at 79.24 mi (127.52 km). The second longest state highway, MD 313 at 75.72 mi (121.86 km), is the state highway that passes through the most counties, five. The longest state highway entirely within one county is MD 235 at 30.63 mi (49.29 km). There are several state highways with lengths of less than 0.50 mi (0.80 km), almost all of which are unsigned. There are several state highways that are split into multiple segments that are signed with the same number but differentiated internally with suffixes. Almost all state highways are constructed and maintained by the Maryland State Highway Administration. The exceptions include all state highways within Baltimore, select segments of state highways that pass through particular cities and towns, a large portion of MD 295 that is maintained by the federal government, and MD 200, a future highway that is being constructed and will be maintained by the Maryland Transportation Authority. The lists of state highways also include former state highways, which are shaded in dark gray in each list.

Since Maryland does not have a secondary route system or county route system, all state highways are part of the main numerical system between 2 and 999. That means the same set of numbers is used for both major highways and minor service roads, and almost every number has been used at one time or another. MDSHA splits segments of highways into primary and secondary highways, but these inventory designations have no bearing on a highway's number.

Maryland has two series of geographical clustering of its route numbers, although there are several numbers within the series that do not follow the sequences. The first sequence runs from 2 to 37. Numbers 2-6 are assigned to highways in Southern Maryland. Numbers 7-10 were originally left out. The sequence continues with 12 on the lower Eastern Shore and heads north through the Eastern Shore and then west through Central and Western Maryland all the way to 37, which was formerly a highway in Garrett County. The second sequence runs from 38 to 378, starting in Garrett County with 38 and passing through Western Maryland, Central Maryland, Southern Maryland, and then north to south on the Eastern Shore to 378 in Worcester County.

Beyond 378, numbers appear to be assigned randomly. In the early days of the route system, numbers above 378 were assigned individually or in groups in order based on when a highway was built. More recently, numbers are assigned based on what is available and numerical relations with an existing route, such as an old alignment sharing the same tens and ones digits as the present highway. For example, MD 732 was assigned to an old alignment of MD 32.

Maryland applies letter suffixes to route numbers as a way of organizing groups of related highways, such as a group of old alignments of a major highway, a group of service roads related to the construction of a major highway, or a combination of both. However, these letter suffixes are only used for inventory purposes and are never signed, with the exception of MD 835A. Since most routes with suffixes are very short highways of low importance, these highways are rarely signed with route markers. However, there are several numbered highways with several disjoint segments whose segments are denoted internally with letter suffixes but the segments are signed with the same numerical route marker; examples of these highways include MD 7, MD 18, MD 144, MD 648, MD 675, and MD 765.

There is no duplication allowed between U.S. and Maryland state highways unless the two highways are related. The only signed example of duplicate numbers is MD 222, which is the old alignment of US 222 before the latter was rolled back from Perryville to Conowingo. Duplication of number is allowed between Interstate and Maryland state highways, but there are no instances where a signed Maryland state highway intersects an Interstate Highway of the same number.