Joe Atkinson is expected to appear before Leeds Crown Court over the death of 24-year-old Poppy Devey Waterhouse.
Miss Devey Waterhouse died of trauma to the head and neck at the couple's home at Saxton Flats, Richmond Hill, on December 14 last year.
Atkinson, 25, a former Wetherby High School pupil, changed his plea to guilty at a hearing last Friday.
Family members of Miss Devey Waterhouse and Atkinson were in court to watch him plead guilty during the emotionally-charged hearing.
Atkinson's parents were among those who broke down in tears.
He had initially denied the offence and had been due to go on trial on June 17.
Atkinson, who has been represented by Richard Wright QC at previous hearings, is listed to appear before Mr Justice Lavender for sentence from 10.30am.
Miss Devey Waterhouse, originally from Frome, Somerset, was pronounced dead at the couple's flat.
Miss Devey Waterhouse and Atkinson met while studying mathematics at Nottingham University, where they both graduated with First Class Honours degrees.
They were keen travellers who shared photos from their trips abroad to countries such as Morocco, Lithuania and Greece.
They spent six months backpacking in South America and the US in 2017 on a trip that Miss Devey Waterhouse wrote on social media would "make or break them".
Other photos show them socialising in bars on Call Lane in Leeds and watching tennis at Wimbledon.
After completing her masters degree in statistics, Miss Devey Waterhouse moved to Leeds with Atkinson and got a job with bookmaker William Hill as a quantitative trading analyst.
An inquest into her death has been opened and adjourned.
A coroner heard in January how paramedics were called to the flat "in relation to an assault by stabbing".
The brief hearing was told that a post-mortem examination revealed that Miss Devey Waterhouse died from "head and neck trauma".