The 26-year-old, who has been at the KCOM Stadium since 2015, was out of contract at the end of this season.
In 2016, the ex-Salford Red Devils and Castleford Tigers man had the highest kick-conversion rate in Super League.
"He's a big part of the group and really seems to have found a home here," said head coach Lee Radford.
"He's tasted some success last season and I know along with the rest of the group he's desperate for some more."
Oldham-born Sneyd came through Salford's academy before spending the 2014 season on loan at Castleford.

It was the 30-year-old's first triumph since a stage win on the 2015 Vuelta a Castilla y Leon and his team's first grand tour stage for two years.
Race leader Tom Dumoulin, who lost time following an unexpected toilet stop on Tuesday, had no such problems again and retained a 31-second overall lead.
Britain's Adam Yates was 30th and is 11th overall with four stages left.
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Rolland prevailed from an 18-man group who broke away 7.8km from the finish of the 219km stage from Tirano to Canazei.
Dumoulin crossed the finish line nearly eight minutes behind Rolland with the main peloton but retains possession of the pink jersey ahead of Colombian rival Nairo Quintana.
1. Pierre Rolland (Fr/Cannondale) 5hr 42min 56sec
2. Rui Costa (Por/UAE Team Emirates) +24secs
3. Gorka Izagirre (Sp/Movistar) Same time
4. Rory Sutherland (Aus/Movistar) Same time
5. Matteo Busato (It/Wilier Triestina) Same time
6. Dries Devenyns (Bel/Quick-Step) Same time
7. Felix Grossschartner (Aut/CCC) Same time
8. Omar Fraile (Sp/Dimension Data) Same time
9. Michael Woods (Can/Cannondale) Same time
10. Julien Berard (Fr/AG2R) Same time
1.  Tom Dumoulin (Ned/Sunweb) 76hrs 05mins 38secs
2.  Nairo Quintana (Col/Movistar) +31secs
3.  Vincenzo Nibali (It/Bahrain)  +1min 12secs
4.  Thibaut Pinot (Fr/FDJ) +2mins 38secs
5.  Ilnur Zakarin (Rus/Katusha) +2mins 40secs
6.  Domenico Pozzovivo (It/AG2R) +3mins 05secs
7.  Bauke Mollema (Ned/Trek) +3mins 49secs
8.  Bob Jungels (Lux/Quick-Step) +4mins 35secs
9.  Steven Kruijswijk (Ned/LottoNL) +6mins 20secs
10. Jan Polanc (Slo/UAE Team Emirates) +6mins 33secs

Derby City Council wanted to shut Moorways Pool from April in a bid to save about Â£350,000 a year.
The Labour-led authority, which needs to save Â£79m over the next three years, said it had found the savings by making cuts in other areas.
Campaigners who gathered more than 4,000 signatures on a petition said they were delighted at the news.
Ranjit Banwait, leader of the authority, said the council had committed to keep it open for a year.
He said the council had identified savings "in back-office areas" and a restructuring of management jobs, which had been "untouched" since 2010.
However, he stressed if the authority failed to get a "fair deal" from central government in the future, the pool would still have to close.
Campaigners had accepted the pool, which is 33m in length, was in need of repair.
There are plans for a new 50m pool to be built by 2018 to replace it.
However, closing it would have left only one other public pool in the city - the Queen's Leisure Centre, they said.
Doug Whitlam, of the Derbyshire Amateur Swimming Association, said: "One of the main things for me would have been the loss of teaching.
"Twelve hundred young people use this facility every week and that would be lost forever."
Half-back Marc Sneyd has extended his contract at Hull FC until the end of 2019 after the club took up a two-year option on his existing deal.
[NEXT_CONCEPT]
Frenchman Pierre Rolland ended a two-year wait for victory by winning the 17th stage of the Giro d'Italia.
[NEXT_CONCEPT]
A Derby swimming pool threatened with closure is to remain open for another year, council bosses have confirmed.