"Donor fatigue" had led to funding for SW Radio Africa drying up, its manager Gerry Jackson told the BBC.
The station was launched when President Robert Mugabe faced strong opposition to his rule from the Movement for Democratic Change (MDC) party.
After four years in coalition with the MDC, Mr Mugabe fended off his rivals and was re-elected to office last year.
Ms Jackson said the long crisis in Zimbabwe, and the "massive disarray" in the ranks of the MDC, had contributed to "donor fatigue".
Seizing radios
The European Union (EU) had also decided to "re-engage with Mugabe and the ruling Zanu-PF party, which may have influenced some donors who do not want a critical voice out there", she added.
BBC World Service Africa editor Richard Hamilton says SW Radio Africa's final news bulletin, from an office outside London, was tinged with sadness.
Although the Zimbabwean government jammed some of its short wave broadcasts, SW Radio Africa still had its loyal listeners - estimated at one point at around one million, he says.
"We are gone so our voice is completely gone," Ms Jackson told the BBC.

Pakistan's military spokesman says the line has just been used for the first time as the two countries work to improve co-ordination along the border.
The move was agreed when Pakistani army chief Raheel Sharif visited Kabul.
Security co-operation between the two countries is seen as crucial in countering the growing Taliban threat.
Earlier this month Afghan President Ashraf Ghani blamed Pakistan-based militant groups for the escalating violence.
Afghan officials often accuse Pakistan of controlling the Afghan Taliban.
The say that Islamabad allows the most senior Afghan Taliban leaders to operate freely there. Pakistan denies this although it admits having contacts with the militants.
News of the hotline comes as Afghanistan will host discussions next week with Pakistan, the US and China to prepare the ground for possible Afghan peace talks involving the Taliban.
Afghanistan sees Pakistani support as crucial if negotiations with the Taliban are to be successful.
President Ghani has recently moved towards strengthening ties with Pakistan - the Taliban's historic supporters - in what correspondents say is a desperate bid to restart peace negotiations as the insurgency spreads.
The president warned that the presence of international militant groups - including al-Qaeda, Islamic State and militant groups from China, Russia, Uzbekistan, Tajikistan and the Middle East - was growing in Afghanistan.
Pakistani Prime Minister Nawaz Sharif said at the beginning of this month that "working for the achievement of a peaceful neighbourhood is a cardinal principal of Pakistan's foreign policy".
"We should envisage collective and co-ordinated measures on the regional security front to ensure that the gains and struggle against terrorism are durable and irreversible," he said.
A radio station opposed to Zimbabwe's government has shut down after 13 years of broadcasting from the UK.
[NEXT_CONCEPT]
Pakistan and Afghanistan have established a hotline between their respective military commanders to reduce frequent cross-border tensions.