The Peugeot 405 is a large family car manufactured by the French automaker Peugeot from 1987 to 1997. Its production continued under license from outside Europe in Iran by Iran Khodro Company until 2020. It was voted European Car of the Year for 1988 by the largest number of votes in the history of the contest. About 2.5 million vehicles have been sold worldwide, both in left and right drive versions, as a saloon and estate. In early 2020, the 33-year production run of the Peugeot 405 was counted as the "twentieth most long-lived single generation car in history."

Its appearance is similar to the Alfa Romeo 164, launched the same year and also styled by Pininfarina. While the 405 shares its floorpan with the Citroën BX, it does not have that car's hydropneumatic suspension, except for the 4x4 version on the rear axle (SRix4, Mi16x4 and T16). As with the BX, the 405 used TU/XU petrol and XUD diesel engines. The 405 was the last Peugeot vehicle sold in the United States, on sale between 1988 and 1991, including the Mi16.

The 405 has been available as a saloon and estate, in front-wheel and four-wheel drive. No coupé model was ever offered, unlike the 504 and later 406: only two examples of the purpose-built, two-door 405 Turbo 16 (not to be confused with 405 T16) were made.

In July 1987, Peugeot unveiled ten versions of the 405 saloon simultaneously for the 1988 model year, with sales on the continent beginning in October 1987 and sales in the United Kingdom beginning in January 1988. It succeeded the long-running Peugeot 305, but also the Chrysler Alpine hatchback and Solara saloon which had been discontinued when the Talbot brand was axed a year earlier. The slightly smaller 305 was discontinued from the Peugeot range soon after the 405's launch, with production of the larger 505 ending a few years later. Peugeot's new range-topping model after 1989 was the larger 605.

Estate sales began in May 1988, although the British market did not receive estate versions until October 1988. No coupé was ever offered to the public, unlike the 504 and later 406. Right hand drive versions being produced at the former plant of Rootes/Chrysler at Ryton near Coventry, and left hand drive production taking place at Sochaux in France.

Four cylinder petrol engines ranging from 1.4 to 1.9 liters and 65 to 160 hp (48 to 118 kW) were available. In 1988, naturally aspirated (1.9) and turbocharged (1.8) diesel engines were added to the range. The 500,000th 405 was produced during 1989, followed by the one millionth 405 to leave the Sochaux factory in 1990. This was also when the BE1 transmission was replaced by the BE3.

In 1991, there were updates to the dashboard, steering wheel, and soundproofing, but for 1992, the Phase II model arrived with a new boot with better ingress, new rear lights and boot design, and a new dashboard. 405 production had reached over 1,500,000 by this time.

In the autumn of 1995, the 405's replacement, the 406 was introduced and the 405 saloon was discontinued. An airbag had been available on the 405 since 1994, and standard on the left hand drive Mi16 and T16. At the beginning of 1997, the estate version of the 406 was launched, marking the end of European 405 production after ten years.