Party leader Richard Di Natale said the proposal would strictly regulate the sale and production of the drug and take it out of the hands of criminal dealers.
He says seven million Australians regularly use cannabis, and all they're doing is feeding the mega profits of criminal syndicates and criminal gangs.
The Greens' plan to legalise cannabis for adult use will feature an Australian Cannabis Agency created to issue licences for production and sale, monitor and enforce regulations, and review the regulatory scheme to make sure it is working properly.
"We need to leave room for the gardaí to tackle real drug trafficking problems with hard drugs, and not criminalise proven medical treatment", said Ms O'Reilly.
The Greens point out that numerous potential objections to cannabis use, such as addiction, teenage access, and clarity on its medical impact, are "not addressed by the current system", and that the party's policy is aimed at achieving "harm reduction".
Senator Di Natale said nearly seven million Australians had tried or used cannabis, with consumption and drug possession-related arrests both on the rise.
A costing by the Parliamentary Budget Office for independent senator David Leyonhjelm, who wants marijuana legalised, found in 2016 that legalising cannabis would generate about $300 million a year in GST revenue, as well as save about $100 million a year in reduced Australian Federal Police and Australian Border Force costs.
The Greens leader, a former drug and alcohol doctor, said Australia's tough approach to drugs had caused enormous harm.
The Greens' policy notes that 35% of Australians have used cannabis, according to Australian Institute of Health and Welfare statistics, and there were 79,643 cannabis related arrests in 2015-16, up 6% from 2014-15.
It would establish a new agency to issue licences for production and sale of the drug, as well as monitor and enforce licence conditions.
"It drives people away from getting help when they need it and exposes them to a risky black market", he said.
Numerous the party's proposed rules for recreational marijuana are similar to those that already apply to the sale of tobacco and alcohol products. The policy would impose strict penalties for anyone caught selling weed on the black market, and for anyone caught driving under the influence. Currently, residents of the ACT can have up to two cannabis plants.
The drug would be available at retail stores in plain packages to people aged over 18, in a plan the party hopes will raise tax for drug treatment programs.
Prominent drug decriminalisation advocate Dr Alex Wodak, who has also fought for legal pill testing at music festivals, has praised the policy.
'Regulating cannabis will give government more control and increase government revenue, which can be used to fund drug prevention and treatment'.