3 Volvo diesel generators RMV Scillonian III is a passenger ship based at Penzance in Cornwall, England, United Kingdom, run by the Isles of Scilly Steamship Company.

As a preferred means of transport between Scilly and the mainland, she is a familiar sight in Penzance and St Mary's, often photographed by tourists and also featured in the BBC series, An Island Parish.

[9] From new in 1977 Scillonian III operated a year-round route through all weather conditions to service the cargo and passenger transport to and from Penzance and the island of St. Mary's, in the Isles of Scilly.

On Saturdays she was scheduled to run a double service leaving earlier in the morning and making a quick turnaround at lunchtime in St. Mary's and then performing a second return voyage in the afternoon.

The Isles of Scilly Steamship Company Ltd. later purchased a smaller cargo vessel purely for freight and Scillonian III was put into maintenance and repair during the winter months.

[12] The annual winter period is used to carry out a maintenance programme, during which Scillonian III is painted and undergoes technical inspections as well as surveys for passenger vessel certification by the Maritime and Coastguard Agency.

This may be the case on busy weekends at the start of the summer season, around the World Pilot Gig Championships, and more regularly during the year when the air services between the Isles of Scilly and the mainland are grounded due to poor visibility (see "Notable events" below).

As air traffic to Scilly was suspended for the day due to poor visibility on the mainland, the government authorities chartered the Scillonian III to make a night sailing from Penzance to bring officials, shipwreck specialists and police reinforcements to St Mary's.

[citation needed] On Monday 12 August 2002, Scillonian III could not sail because of a technical fault, leaving hundreds of tourists temporarily stranded on St Mary's.

Freight services to St Mary's were also disrupted by the cancellation, so Gry Maritha had to make a rescheduled Monday night sailing to deliver fruit and vegetables to the Isles of Scilly.

[19] On 2 May 2011, the cancellation of a Scillonian III sailing on the bank holiday after the World Pilot Gig Championships weekend left visitors stranded on St Mary's.

Scillonian III departed for the first sailing as planned, but with weather conditions worsening in the strong Easterlies and waves crashing onto the pier in Penzance it became unsafe to berth and she had to spend three hours circling in Mount's Bay, waiting until high tide with 450 passengers on board.

When the second sailing was then cancelled, council staff opened up emergency accommodation at their Carn Thomas offices and Town Hall to provide shelter for visitors stranded on St Mary's.

[22] On 24 May 2013, Scillonian III ran aground in St Mary's Harbour after being caught by a gust of wind, while attempting to berth by normal approach at low tide.

[23][24] On Wednesday 28 August 2019, Scillonian III had to return to Penzance after she suffered a technical fault mid-crossing which caused the ship to be out of service for four days, leading to significant travel disruption between the islands and mainland.

Engineering teams in Penzance undertook a complex strip down and rebuild process to access and carry out repairs, complicated and further delayed when one of the replacement parts delivered was found to have a hairline fracture and had to be reordered.

[25][26][27] The Isles of Scilly Steamship Company issued a statement praising residents and businesses on the islands and its own team members, ″for the way they have pulled together in what have been unprecedented circumstances to deal with the issue, support passengers and ensure no one on the islands has been left without proper accommodation.″ The Scillonian III returned to service on Sunday 1 September 2019 and completed a double sailing on Monday 2 September 2019, clearing the backlog of affected passengers.

The Isles of Scilly Steamship Group signed contracts with French shipbuilding company Piriou in January 2024 for the construction of both the Scillonian IV and a new freight vessel.