Short answers, pulled from the story.
Oh My Goddess! was written and illustrated by Kōsuke Fujishima. It was serialized in Kodansha's seinen manga magazine Monthly Afternoon from September 1988 to April 2014, spanning 308 chapters collected in 48 tankōbon volumes.
As of June 2020, the manga had over 25 million copies in circulation. It also won the 33rd Kodansha Manga Award in the general category in 2009.
College sophomore Keiichi Morisato accidentally dials the Goddess Help Line and meets the goddess Belldandy, who grants him a single wish. He wishes she will stay with him forever, and the two take up residence in a Buddhist temple, later joined by Belldandy's sisters Urd and Skuld.
The two titles reflect different translation choices. AnimEigo chose Oh My Goddess! for the OVA, and Dark Horse Comics followed for the manga in 1994; translator Toren Smith confirmed with Fujishima that "Oh" matched the author's intent. Kodansha's bilingual edition and Pioneer's film release used "Ah! My Goddess", so both titles appeared in the market simultaneously.
The series was adapted into a five-episode original video animation directed by Hiroaki Gōda, released between February 1993 and May 1994. A full TV series aired from January to July 2005, followed by a second season in 2006, a two-episode anniversary special in December 2007, a 48-episode comedy spin-off (The Adventures of Mini-Goddess) from 1998 to 1999, and a theatrical film in 2000.
Banpresto released an adventure game for the NEC PC-9801 in 1993, with an enhanced port for the PC-FX in 1997. A Dreamcast quiz game appeared in August 1998. Marvelous Interactive released a PlayStation 2 game in February 2007, available only in Japan in both standard and limited "Holy Box" editions.