BoxRec

Only counting cases where the title was both won and lost in the ring.

Eduardo Ray Marquez recently managed a reign as WBO Strawweight Champion of just 36 days

Fri 28 Mar 2003 TKO 10 Jorge Mata
Sat 3 May 2003 L TKO 9 Ivan Calderon

Does anyone know of any boxer who spent a shorter total time as title holder?

Tony Canzoneri's second reign as World Light Welterweight Champion lasted just 33 days

Sun 21 May 1933 W 10 Battling Shaw
Fri 23 Jun 1933 L MD 10 Barney Ross

Doess anyone know a shorter single title reign?

Tony Canzoneri's second reign as World Light Welterweight Champion lasted just 33 days

This is inIMO the shortest rein won and lost in the ring.
Followed by

Terry Norris WBC / IBF light-middleweight title 42 days

I just found an even shorter reign, Mike Glover spent just 21 days as World Welterweight Champion

Tue 1 Jun 1915 W 12 Matt Wells
Tue 22 Jun 1915 L 12 Jack Britton

The Welterweight championship had a number of very short reigns about then, Waldemar Holberg reigned for 23 days

Thu 1 Jan 1914 W 20 Ray Bronson
Sat 24 Jan 1914 L DQ 6 Tom McCormick

Tom McCormick then managed just 56 days

Sat 24 Jan 1914 DQ 6 Waldemar Holberg
Sat 21 Mar 1914 L 20 Matt Wells

Somewhat earlier Matty Matthews's first reign lasted 49 days

Tue 17 Apr 1900 KO 19 Mysterious Billy Smith
Tue 5 June 1900 L 25 Eddie Connolly