Branching to sinuous ridges systems, hundreds of kilometers in length and comprising layered strata, are present across much of Arabia Terra, Mars. These ridges are interpreted as depositional fluvial channels, now preserved as inverted topography. Here we use high‐resolution image and topographic data sets to investigate the morphology of these depositional systems and show key examples of their relationships to associated fluvial landforms. The inverted channel systems likely comprise indurated conglomerate, sandstone, and mudstone bodies, which form a multistory channel stratigraphy. The channel systems intersect local basins and indurated sedimentary mounds, which we interpret as paleolake deposits. Some inverted channels are located within erosional valley networks, which have regional and local catchments. Inverted channels are typically found in downslope sections of valley networks, sometimes at the margins of basins, and numerous different transition morphologies are observed. These relationships indicate a complex history of erosion and deposition, possibly controlled by changes in water or sediment flux, or base‐level variation. Other inverted channel systems have no clear preserved catchment, likely lost due to regional resurfacing of upland areas. Sediment may have been transported through Arabia Terra toward the dichotomy and stored in local and regional‐scale basins. Regional stratigraphic relations suggest these systems were active between the mid‐Noachian and early Hesperian. The morphology of these systems is supportive of an early Mars climate, which was characterized by prolonged precipitation and runoff. Plain Language Summary Landscape features identified as former rivers and lakes are common across ancient Martian surfaces (>3.7 billion years ago), strong evidence for an ancient hydrologic cycle. However, the nature of the ancient climate and environment remains unclear and detailed investigations of Mars's geology are necessary to help constrain this. Using high‐resolution satellite images, we investigate a series of sinuous ridges preserved at the Martian surface throughout the ancient Arabia Terra region. These sinuous ridges often occur downslope of river valleys, commonly as the valleys enter topographic basins. The ridges are usually found on the oldest exposed geological surfaces. The morphology of the ridges and their relationship to river valleys suggests that they are sedimentary rocks, which form in or next to rivers. We interpret the basins as ancient lakes and their associated deposits as lake sediments. These rivers were active ~3.7 billion years ago and transported and deposited sediment through the Arabia Terra region. On Earth, rivers typically take between 50,000 and 1,000,000 years to develop such thick deposits. These river deposits are now exposed as ridges due to erosion. The formation of these rivers and lakes in Arabia Terra was likely due to prolonged and episodic precipitation‐driven erosion. Key Points Fluvial depositional systems, 50–100 m in stratigraphic thickness, are common across Arabia Terra, Mars These deposits represent former rivers (at least 100–200 km long), floodplains, and lakes and are found filling fluvial valleys and basins These systems are mid‐Noachian to early Hesperian in age and represent significant periods of geologic time