It flows through the Australian state of New South Wales and the Australian Capital Territory, descending 1,500 metres (4,900 ft) over 1,485 kilometres (923 mi),[2] generally in a west-northwesterly direction from the foot of Peppercorn Hill in the Fiery Range of the Snowy Mountains towards its confluence with the Murray River near Boundary Bend.

[11] The river's headwaters arise from the wet heath and bog at the foot of Peppercorn Hill situated along Long Plain which is within the Fiery Range of the Snowy Mountains; and about 50 kilometres (31 mi) north of Kiandra.

The Murrumbidgee drains much of southern New South Wales and all of the Australian Capital Territory, and is an important source of irrigation water for the Riverina farming area.

In 1820 the explorer Charles Throsby informed the Governor of New South Wales that he anticipated finding "a considerable river of salt water (except at very wet seasons), called by the natives Mur-rum-big-gee".

[20] In 1823, Brigade-Major John Ovens and Captain Mark Currie reached the upper Murrumbidgee when exploring south of Lake George.

His description of wild strong currents in the Murrumbidgee—in the middle of summer (14 January 1830), when flows are declining and close to the seasonal summer/autumn minimum, is in contrast to the reduced flow seen at the junction today in mid-summer: The men looked anxiously out ahead; for the singular change in the river had impressed on them an idea, that we were approaching its termination ... We were carried at a fearful rate down its gloomy and contracted banks ... At 3 p.m., Hopkinson called out that we were approaching a junction, and in less than a minute afterwards, we were hurried into a broad and noble river ... such was the force with which we had been shot out of the Morumbidgee, that we were carried nearly to the bank opposite its embouchure, whilst we continued to gaze in silent astonishment on the capacious channel [of the Murray River] we had entered ...The Murrumbidgee basin was opened to settlement in the 1830s and soon became an important farming area.

It is scarcely probable that Meehan and Hume, who on this occasion were within comparatively easy reach of the head waters, could have seen a new inland river at that time without mentioning the fact, but there is no record traceable anywhere as to the date of its discovery, or the name of its finder.

When in 1823 Captain Currie and Major Ovens were led along its bank on to the beautiful Maneroo country by Joseph Wild, the stream was then familiar to the early settlers and called the Morumbidgee.

From all this we may deduce the extremely probable fact that the position of the river was shown to some stockrider by a native, who also confided the aboriginal name, and so it gradually worked the knowledge of its identity into general belief.

To allow the steamers and towed barges to pass, there were opening bridges at Hay, Balranald, and Carathool[24][25] The river has risen above 7 metres (23 ft) at Gundagai nine times between 1852 and 2010, an average of just under once every eleven years.

The ordering of the basin, from source to mouth, of the major tributaries is: The list below notes past and present bridges that cross over the Murrumbidgee River.