Jack's Restaurant (or Jeanty At Jack's) is a historic building and a former restaurant in the Financial District of San Francisco, California. Opened in 1863, Jack’s was the third oldest restaurant in the city, following Tadich Grill and The Old Clam House.

It has been listed as a San Francisco Designated Landmark since 1981.

In 1863. French-born chef George Voges opened the restaurant at 615 Sacramento Street, and named it Jack's after the jackrabbits that lived nearby. From 1996 until 1998, the building was closed for renovations and a seismic retrofit. The sixth owners were restaurateurs Gus and John Konstin, who re-opened the restaurant in 1998.

In 2002, French-born chef Philippe Jeanty purchased Jack's, later renaming it Jeanty at Jack's, and operated it as a brasserie, until it abruptly closed in May 2009.

In June 2016, Bar Works purchased the building for a reported US$3.55 million, announcing plans to convert the location into co-working space, with food and a bar. As of 2022 that had not materialized.

• List of the oldest restaurants in the United States