Voters in the NSW seats of Bega, Monaro, Strathfield and Willoughby are heading to the polls to vote in new representatives in the so-called Super Saturday by-elections, triggered by a wave of resignations from the state parliament.

Polling booths opened at 8am and close at 6pm.

Postal votes, offered to all constituents in the seat as a COVID-19 precaution, must also be completed by 6pm, but voters have until Febraury 25 to mail them in.

BEGA:

The south coast electorate has never been held by a Labor candidate, and the Liberals won it at the last election with a margin of 6.9 per cent.

The by-election was triggered by the resignation of former transport minister Andrew Constance, who is now running for a seat in federal parliament.

Key candidates include:

* Michael Holland, Labor: A gynaecologist and obstetrician campaigning on improvements to rural health and social housing.

* Fiona Kotvojs, Liberal: A former teacher turned farmer who has unsuccessfully run for the Liberals in a local federal seat.

* Victor Hazir, Shooters, Fishers and Farmers Party: The secretary of the Taxi Owners Small Business Association of NSW.

STRATHFIELD:

The seat in inner west Sydney was held by the former leader of NSW Labor Jodi McKay, who left politics in 2021, months after she was pressured into quitting as party leader.

Labor previously held Strathfield with a margin of five per cent, but current leader Chris Minns says keeping the seat will be difficult for the party.

Key candidates include:

* Jason Yat-sen Li, Labor: A former United Nations lawyer turned investment firm chairman.

* Bridget Sakr, Liberal: A businesswoman who came into the spotlight when a drunk and drugged driver killed her 11-year-old daughter and her three cousins in Oatlands.

* Elizabeth Farrelly, independent: A Sydney Morning Herald columnist who has campaigned on property development reform.

MONARO:

The seat of Monaro is up for grabs after NSW deputy premier and Nationals leader John Barilaro resigned in October.

Mr Barilaro won the seat from Labor in 2011, and increased his margin to 11.6 per cent at the last election.

Key candidates include:

* Nichole Overall, Nationals: A journalist, historian and Queanbeyan local.

* Bryce Wilson, Labor: Another Queanbeyan local, who works as an electorate advisor.

* Andrew Thalor, independent: A former manager of a scrap metal business, who in 2015 had an unsuccessful tilt at a seat in the NSW Upper House.

WILLOUGHBY:

The blue-ribbon lower north shore seat was held for almost two decades by former premier Gladys Berejiklian, who resigned under a cloud of corruption allegations in October.

The seat is considered to be a very safe Liberal seat, with Ms Berejiklian winning it with a margin of 21 per cent last election. Labor is not running a candidate.

Key players include:

*Tim James, Liberal: A former Liberal staffer and the executive director of the Menzies Research Centre think tank.

* Lynne Saville, Greens: A registered nurse and former lecturer, who has served on Willoughby Council for 18 years.

* Penny Hackett, Reason Party: A prominent voluntary assisted dying campaigner, who lists schools, health and aged care and sustainable development among her key issues.

Australian Associated Press