We have had lots of military dictatorships, but I cannot recall of the top of my head a Naval one. In one British history book, it’s stated that the primacy of the RN post 1692 is one reason the UK never fell to rule by the armed forces, the military was too small and the Navy too inherently unable to seize power.
How do you define Naval Dictatorship?
From wikipedia:
This guy was commander in chief of the Navy and part of the coup.
And this guy was an admiral and sort of dictator.
The Greek navy attempted a coup d’etat in 1973 to overthrow the existing Army dictat under Papadopolous and restore the monarchy (which was itself mostly autocratic).
I came into this thread specifically to point to Adm. Horthy. Although what he led was a right-wing counterrevolution to the Socialist dictatorship of Bela Kun, and he cloaked himself in the title of Regent for the King of Hungary, the actual claimants to the throne, Karl IV (1920-22) and Otto II (1922-44, continuing as pretender until his death in 2011) were barred by law from entering Hungary, and he ruled, with the SS-equivalent Black Arrowhead as his paramilitary power source, as effective dictator until he saw Hitler’s end nearing and tried making a se[arate peace with the USSR.
Admiral Karl Donitz was briefly the successor to Hitler in the final days of the Third Reich, if that counts
I think you’re referring to the Arrow Cross party. If you are, I don’t think that’s an accurate description of Horthy’s regime. Horthy was an old-fashioned conservative authoritarian who had no love for the Hungarian fascists.
IIRC, wasn’t the ruling council of Argentina composed of all military branches?
One story says that during the Falklands war, the navy got upset that the army and air force were getting all the credit and glory. There was a noisy showdown in the cabinet room, the head of the navy said “you can’t tell me what to do”, ordered the Belgrano battleship out of harbour in contradiction of the orders of the president, and it was promptly sunk like a sitting duck.
Given that Hungary is a landlocked country, it always seemed to me that Admiral Horthy became its dictator for want of anything else to do.
Hey, maybe! Hungary lost its last sea access in 1920 in the Treaty of Saint-German, the same year as Horthy’s “regency” began. 
It was either that or hire some nun to teach the kids how to sing…
Can we include Scientology?
i find the original question a little vague. An admiral is just a flag-rank officer who likely has very high access within the government. If he’s the guy who pulls a gun instead of a general, does that make it a “naval dictatorship”? I’d say not.
Is there a case where the navy was the armed forces who physically took control and provided security, control, etc.? That would define a “naval dictatorship” more than the specific rank of the bigwig who grabbed the bigger wig.
It’s not the “specific rank”. It’s who answers to it. Soldiers are not likely to follow a naval officer who deposes the sitting leader, regardless of his rank.
A Russian Navy admiral (Adm. Kolchak) was briefly the leader to the "White " Russian government (in the 1918-1920 Civil war).
I’d say that the Japanese militarist regime is a pretty good rebuttal of the claim in the OP. Like the UK, Japan was an island nation that primarily looked to its world class navy for security instead of its rather middling army, but that didn’t stop the military from seizing power. You could probably describe that regime as being at least a quasai-naval dictatorship given the large role the navy had in it, although the generals were ultimately the ones in charge.
Commodore Bainimarama is a naval officer, but was head of all the armed forces when he took over Fiji back in 2006.
Nitpick: Hungary’s post WWI borders were set by the Treaty of Trianon.
We can’t assume that a military leader who leads a coup is trying to make himself a dictator. Admiral Larrazabal led a coup in Venezuela in 1958 against a real dictator, Marcos Perez Jimenez. Larrazabal then served as president less than a year, resigned to run for the office in democratic elections, lost, and abided by the results. I have never heard that he was particularly dictatorial during his brief time in the presidency.