San Francisco Supervisor Mark Farrell announced Thursday that he will not enter the mayor’s race, putting an end to months of speculation about whether he would consider running.

In an email to his supporters, Farrell cited a desire to spend more time with his wife and three young children.

“The timing is simply not right for our family, and I will always put them first,” he said.

Farrell said he has long maintained that any future political decisions “would be made through the lens of my family, period. The fact is, I’m not willing to disappear from my family for the next six months during the course of a compressed mayoral campaign,” he said in an interview.

The June 5, 2018, ranked-choice mayoral election was scheduled after Ed Lee’s sudden death Dec. 12.

Instead, Farrell said he would spend the rest of his time in office “addressing the quality-of-life issues that matter most to San Franciscans: homelessness, housing and public safety,” he said in his email.

Farrell is also spearheading an ambitious initiative to create a city-owned fiber optic Internet network connecting every resident and business in San Francisco to high-speed Internet service. Next year will be “instrumental,” Farrell said, for pushing that project “toward reality.”

Before his election to the board in 2010, Farrell worked as a corporate attorney in Silicon Valley and later spent five years as an investment banker. He’s also a co-founder of Thayer Ventures, a venture capital firm in San Francisco that invests in companies in the hospitality and travel sectors. He was re-elected as the city’s District Two supervisor in 2014 and will be termed out of office in 2018.

The field of potential mayoral candidates is expected to swell in the coming weeks, as the Jan. 9 deadline to file nomination paperwork draws closer. This week, Supervisor Jane Kim, former Supervisor Angela Alioto and a handful of lesser-known candidates have pulled papers to run for mayor.

Ten hopefuls have requested nomination forms from the city Department of Elections so far. They will not be official candidates until those forms are completed and returned.

Farrell said he intends to take a “wait-and-see approach” on whom he intends to support in the mayor’s race. “There’s a long way between now and when the field is finalized,” he said.

“At this point, all options are on the table.”

Dominic Fracassa is a San Francisco Chronicle staff writer. Email: dfracassa@sfchronicle.com Twitter: @dominicfracassa