It connects Balard in the southwestern part of Paris to Pointe du Lac station in the southeastern suburbs, following a parabolic route on the Rive Droite of the Seine.

The last line of the original 1898 Paris Métro plan, which opened in July 1913, it was initially intended to link Porte d'Auteuil and Opéra.

The current route serves the southwestern part of the city, the Grands Boulevards and Bois de Vincennes, ending in the southeastern inner suburbs through the communes of Charenton-le-Pont, Maisons-Alfort and Créteil, which the line reached in 1974 at Créteil–Préfecture station, after several extensions.

The project would connect Opéra with Porte d'Auteuil via Grenelle with a shuttle, similar to the network's other lines.

[1] Construction of the underwater crossing of the Seine began in April 1908 between the Concorde and Invalides stations, at the level of Pont Mirabeau.

Although metal caissons were originally planned to be sunk vertically (as had been done on Line 4), a tunnel was drilled following a single circular tube with the aid of a shield; authorities opposed the first method because of the risks to boating.

Before the completion of work near Pont Mirabeau, the line opened to the public on 13 July 1913 between Beaugrenelle and Opéra; the extension to Porte d'Auteuil followed on 30 September.

As part of the extension, a common route with Line 9 between the Richelieu – Drouot and République stations was planned in order to limit the impact of this problematic section on street traffic.

Located on the former course of the Seine, the ground is soft and the initial plan to build two parallel tunnels generated lengthy controversy.

The extension of the line to Porte de Charenton, including the construction of seventeen 105-metre stations, was agreed on 25 March 1924[8] and work began in 1928.

The Line 8 stations are on the upper level: two half-stations, separated by a central supporting wall to ensure stability.

The 7.8 km (4.8 mi) extension was completed in March 1931 and opened to the public on 5 May, ending at Porte de Charenton.

The extension required crossing the Marne on a viaduct, since the Charenton – Écoles station was at the edge of a cliff north of the river.

[10] Créteil became a prefecture after the creation of the department of Val-de-Marne, resulting in an increase in population, and a new extension was quickly begun in several stages.

[14] This was the first Paris Métro connection with the prefecture of a bordering department, extending the line to over 22 km (14 mi) and 37 stations.

[16] The extension of line 8 south of Créteil-Préfecture, over 1.3 km (0.81 mi) to Pointe du Lac station was opened on 8 October 2011.

[17] It was approved by the launch of the preliminary project and the financing agreement by the STIF council, the transport organising authority in Île-de-France, during its meeting of 20 September 2006.

The Champ de Mars station, between La Motte-Picquet – Grenelle and École Militaire, was closed on 2 September 1939.

[23] After the Champ de Mars ghost station the line serves École Militaire and La Tour-Maubourg, curving right and left under the Invalides esplanade and beginning a .04-percent descent under the park tracks and the main tracks of Line 13 to the Invalides station under the Rue de Constantine.

It crosses Line 14, passing the Clichy sewage-treatment plant to Opera before skirting the Grands Boulevards to Richelieu – Drouot.

[24] Both lines reach the same level at République, via Grands Boulevards, Bonne Nouvelle, Strasbourg – Saint-Denis and the closed Saint Martin station.

[25] The line continues under the Grands Boulevards to Bastille, via Filles du Calvaire, Saint-Sébastien – Froissart and Chemin Vert.

[11] Line 8 reaches Montgallet on a .04-percent grade before the Bois de Vincennes, via the Daumesnil, Michel Bizot and Porte Dorée stations.

The line then turns southeast, leaving Paris to cross the commune of Charenton-le-Pont via the Liberté and Charenton – Écoles stations.

Richelieu–Drouot has a black marble war memorial dedicated to metropolitan railway employees mort pour la France, sculpted by Carlo Sarrabezolles in 1931.