The citadel of Pamplona, also known as the New Castle, is a Renaissance fortification that was formerly used for military purposes and was constructed in Pamplona, the Autonomous Community of Navarre's capital, between the 16th and 17th centuries. Today, the castle's buildings are used for cultural events and a sizable portion of it serves as a garden.

Since 8 February 1973, it has been recognised as a National Historic-Artistic Monument (Bien de Interés Cultural).

12 It received the special prize from the general population as well as the Europa Nostra Cultural Heritage Prize for "Conservation" in 2012 from the European Union.

As part of a plan for the comprehensive rebuilding and bolstering of the city's defences, Philip II ordered its construction in 1571. Giacomo Palearo, a military engineer known as "el Fratin," designed it; viceroy of Navarre Vespasiano Gonzaga y Colonna also contributed to the project. They developed a defence strategy in line with Italian Renaissance theory, which had recently been implemented in the city of Antwerp, where Francesco Paciotto, who also designed the citadel of Turin, had built the citadel. It was enclosed in a five-pointed star form. From each of the sites, it was feasible to control every conceivable attack angle. In 1569, engineer Antonelli wrote to Philip II that "Pamplona is now more of a frontier than a metropolis... it must have a very important castle, because as the memory of the government of its natural king is still fresh... it is still necessary to ensure the strength of its wills... The work must serve to defend itself from extrinsic, but also internal threats. It should not be forgotten that the Kingdom of Navarre had recently been conquered, with bouts of reconquest involving the population's active participation. The Citadel "must be understood as a way of dominating a city from which a rebellion was to be expected," writes Alicia Cámara in her book Muraria, and the Venetian ambassador Contarini forewarned that "all the people of this kingdom hate the Spaniards and want their natural king Juan de Albret to return."

San Antón, El Real, Santa Mara, Santiago, and La Victoria are the names of the bastions.

Although exterior "half-moons" were added in 1685 and the first half of the 18th century, it can be said to have been finished in 1645. This strengthened the defensive system.

This reinforcement was based on a Juan de Ledesma project that used the polyorcetic method called "de Vauban"—named for the military engineer who revolutionised military engineering during the reign of Louis XIV. Between the San Antón and El Real bastions (facing the San Nicolás gate) and the bastions of Santiago and La Victoria (facing the Taconera gate), two half-moons were constructed. The counterguards that were built to surround the Santiago, Santa Mara, and El Real bastions on both sides increased their ability to defend themselves.

No noteworthy defensive incidents have occurred in the Pamplona citadel. Because of this, although it was seized, it was rarely besieged. Napoleon's French army, led by General D'Armagnac, captured Portugal on February 16, 1808, using a straightforward trap. D'Armagnac had been granted permission to enter the Iberian Peninsula and invade Portugal by King Charles IV as part of the Treaty of Fontainebleau. His forces arrived on February 9, 1808, through the San Nicolás gate (located in what is now the Segundo Ensanche at the intersection of Calle Cortes de Navarra and Calle San Ignacio). Up to 4,000 soldiers were quartered in various locations, with the officers staying in the nobles' homes in the city. Unrest in this situation resulted in a street brawl that left one of the soldiers stabbed to death. Napoleon gave D'Armagnac the order to seize the citadel in an increasingly hostile environment. When it snowed on February 16, the French soldiers amused themselves as they approached the citadel by throwing snowballs at one another, much to the amusement of the defenders. They prepared their concealed weapons when they were close, entered the citadel, and captured it.

Similar tactics were successful in other subsequent captures of citadels and castles (the citadel of Barcelona and Montjuic Castle by Duhesme on February 28, the citadel of Figueras by Colonel Piat, and the castle of La Mota in San Sebastián by Duhesme) against the Napoleonic forces.

The army of the Hundred Thousand Sons of Saint Louis faced off against the Liberal soldiers in 1823, and they held out for five months. While the rest of the army moved across the peninsula to reestablish absolutism, the goal was to besiege it without taking it in order to stop the soldiers from escaping. They then started a bombardment on September 3 that also hit Pamplona. They gave up on September 16 following more heavy bombardment.
In honour of those killed in Pamplona during the Civil War, a monolith was erected in March 2012.

At the Puerta del Socorro gate, behind the monument, the rebels executed many Republicans during the Spanish Civil War as part of a very harsh repression in Navarre. In March 2012, a monolith with the same text was installed in the area of the moats close to the Socorro Gate to replace the plaque that had been erected in their honour back in 20075. The inscription reads as follows in both Spanish and Basque:

The 298 citizens who were killed in 1936 for standing up for freedom and social justice were honoured by the city council and the city of Pamplona.

Franco's forces utilised the Citadel between 1937 and 1939 as a component of the Pamplona prisoner concentration camp complex, the main camp of which was situated in the convent of La Merced.

A very well-liked park with cultural uses was created in the former military buildings in 1964, when the area lost its military identity.

After the city received the fortified enclosure, some of the structures inside the park were preserved:

The 1694 Torelli powder magazine.
The mixtures storage facility that Ignacio Sala renovated in 1720.
Weapons Room, built in 1725 by the architect Jorge Próspero de Verboom, who also built Barcelona's citadel.

The largest green space in Pamplona, Vuelta del Castillo Park, which was left undeveloped for centuries due to defensive reasons, surrounds the structure on all sides. It is now situated in the city's center.

After the official transfer of ownership of the historical Citadel complex, which covers a total area of 275,840 m2, to the city, including the exterior spaces, Following a citywide consultation in 1971, it was decided to keep the Citadel and the surrounding land as a "green area with restored historic buildings," which was favoured over plans to turn the area into a small "medieval city," develop it as a sports venue, or leave it entirely as a green space.

In order to preserve the surrounding of the fortification, the City Council proposed in 1972 that the location of the former Artillery barracks—near Calle Yanguas y Miranda, at the eastern end of the Citadel, where the Bus Station now stands—be left undeveloped. In December, the council also applied to the government to have the entire complex designated a National Historic-Artistic Monument, which was accomplished by Decree 332/1973 of February 8, 1973.

The Citadel was originally a perfect pentagon with five points, but in the late 19th and early 20th centuries the San Antón and La Victoria bastions—the two facing the city—were partially destroyed to make room for the construction of the Primer Ensanche, which included some homes and new barracks outside the walls, as well as the Avenida del Ejército in 1971, which gave the Citadel its current shape. The exterior wall was renovated this year, with the stonework being cleaned and any damaged or altered components being repaired.

On the remnants of the San Antón Bastion, the Navarrean Congress Center and Auditorium, also known as the Baluarte, was constructed. In November 2007, work on the new Pamplona Bus Station, which is situated close to the Citadel and beneath the glacier, was also completed.