Voiced by: Saori Hayami (Japanese); Brittney Karbowski (English)
The title character and main heroine of the series, Ikaros is a beautiful gynoid known as an Angeloid. She falls from the sky at the beginning of the story. After Tomoki recovers her, she forms a bond with him and calls him master: the imprinting is symbolized by a chain from her collar to his hand. She has an expressionless face that makes the other characters wonder if she will ever smile. Her emotions develop slowly, due to her programmed setting of high battle abilities and high processing abilities but low emotional abilities. Despite this, she develops genuine feelings of love for Tomoki. She also goes along with any of his perverted schemes, and eventually burns up into nothing after carrying Tomoki to Synapse, showing him her smile for the first time. She and the others are later resurrected by Tomoki's final wish. Although she initially states she is a "Pet-Class" (entertainment-purposed) Angeloid, she is actually a "Strategic Battle-Class" Angeloid. In her previous visit to Earth as the Uranus Queen, she destroys the Tower of Babel. In "Battle Mode", she employs: Aegis, an energy shield sphere; Artemis, which fires an array of energy projectiles from her wings; and Apollon (アポロン, Aporon, from the Greek Apollyon), a bow that fires an arrow of mass destruction. In Uranus Queen mode, she can interface with massive weapons platform called the Uranus System (Hephastus System in the Funimation dub). In a later battle, she evolves into Ikaros Version II with "Dual Variable Wings" that boost her power. Her name comes from the Greek mythological character Icarus, a craftman's son who flew too close to the sun and fell from the sky.

Heaven's Lost Property began monthly serialization in the May 2007 issue of Shōnen Ace sold on March 26, 2007 and concluded with the March 2014 issue sold on January 26, 2014. The first tankōbon was released by Kadokawa Shoten on September 26, 2007, with a total of 20 tankōbon released in Japan. Chapter titles are often suffixed with two exclamation points.

In addition, a four-panel comic, titled Sora no Otoshimono Pico (そらのおとしものPICO, Sora no Otoshimono Piko), illustrated by ms, was developed and published in the inaugural issue of Kadokawa Shoten's 4-Koma Nano Ace magazine (published on March 9, 2011), and continued in Shōnen Ace until its conclusion on March 26, 2011. It focuses on the lives of Astraea, Nymph, and Ikaros.

An anime adaptation produced by AIC and directed by Hisashi Saitō aired in Japan from October 4 to December 27, 2009 on TV Saitama and Chiba TV, with subsequent broadcasts on KBS, tvk, Sun Television, TVQ, Tokyo MX and TV Aichi, with English-subtitled simulcasts provided on the Crunchyroll. Seven DVD compilation volumes were released between December 25, 2009 and June 25, 2010 by Kadokawa Pictures, with limited edition volumes also sold. A Blu-ray box set was released on June 24, 2011. An OVA episode entitled "Project Pink" was bundled with the limited edition release of volume 9 of the manga on DVD on September 9, 2010.

A second season, Sora no Otoshimono: Forte (そらのおとしもの（フォルテ）), was announced on reprinted copies of the manga, and aired 12 episodes between October 1 to December 17, 2010 with simulcasts provided by Crunchyroll, as with the first season. Six DVD volumes were released by Kadokawa Pictures between December 24, 2010 and May 27, 2011.

The opening theme for the first season is "Ring My Bell", and for the second season, it is "Heart no Kakuritsu" (ハートの確率, Hāto no Kakuritsu, "Probabilities of the Heart"); both are performed by Blue Drops and feature singers Hitomi Yoshida and Ikaros (Saori Hayami). Both seasons also use different ending themes for each episode.

Both seasons of the anime are licensed in North America by Funimation Entertainment, which released them under the respective titles of Heaven's Lost Property and Heaven's Lost Property: Forte. The first season was released on December 20, 2011 on DVD and Blu-ray. However, due to concerns from the Japanese licensing company regarding Blu-ray sales, the second season was released only as a 2-disc DVD set in North America on March 20, 2012. The second season was released on Blu-ray on June 25, 2013.

A film adaptation called Sora no Otoshimono the Movie: The Angeloid of Clockwork (劇場版 そらのおとしもの 時計じかけの哀女神（エンジェロイド）, Gekijōban Sora no Otoshimono: Tokei-jikake no Enjeroido) was announced by Kadokawa Shoten in November 2010. The film focuses on the Hiyori arc of the manga. A 30-second teaser trailer was shown in the post-end credits of the final episode of Forte. The film premiered in Japanese theaters on June 25, 2011. Funimation Entertainment licensed the film under the title of Heaven's Lost Property the Movie: The Angeloid of Clockwork, and released it on February 26, 2013. A second film called Heaven's Lost Property Final – The Movie: Eternally My Master was released on April 26, 2014.