The Wonderful Parliament was a session of the English parliament held from October to November 1386 in Westminster Abbey. Originally called to address King Richard II's need for money, it quickly refocused on pressing for the reform of his administration. The King had become increasingly unpopular because of excessive patronage towards his political favourites combined with the unsuccessful prosecution of war in France. Further, there was a popular fear that England was soon to be invaded, as a French fleet had been gathering in Flanders for much of the year. Discontent with Richard peaked when he requested an unprecedented sum to raise an army with which to invade France. Instead of granting the King's request, the houses of the Lords and the Commons effectively united against him and his unpopular chancellor, Michael de la Pole, 1st Earl of Suffolk. Seeing de la Pole as both a favourite who had unfairly benefited from the King's largesse, and the minister responsible for the King's failures, parliament demanded the earl's impeachment.

At first, the King refused to attend the parliament, instead attempting—unsuccessfully—to dissolve the sitting. Richard requested the Commons send a delegation to negotiate with him at Eltham Palace; they, fearing an ambush, sent two lords instead. One of them, the Duke of Gloucester (Richard's uncle) threatened Richard with deposition unless the King agreed to return to Westminster and do parliament's bidding. He was forced to sack the unpopular de la Pole and was restricted to advisers vetted and appointed by parliament. The King was incensed at what he perceived to be an unnatural restriction on his God-given right to appoint his own ministers and advisers; he left Westminster almost immediately. He spent much of the following year gathering support, ignoring his parliament-imposed council, and taking legal advice on how to annul the constraints on his rule. During this time de la Pole was returned to royal favour. Although the King managed to overturn most of the restrictions the Wonderful Parliament placed upon him, within a few years the crisis had resurged, even worse than in 1386. Armed conflict broke out between crown and nobility, eventually resulting in de la Pole's exile, and the execution of many of his supporters.

In 1386 ... when the king should have first blossomed into manhood, a certain archbishop of York called Alexander Neville, Robert de Vere, Duke of Ireland, Michael de la Pole, earl of Suffolk and chancellor of England, Robert Tresilian, the king's chief justice, and Sir Nicholas Brembre, formerly mayor of the city of London, were the king's rulers and closest advisers. They were men of vicious character who deceived the king, having an eye to the business neither of the king nor kingdom, but they grasped to themselves the riches of iniquity by many evil deeds. The impoverished king was put into the shadow of their sin, and so the realm was smitten by the levying of a great plague of tenths and subsidies.

Richard II succeeded to the throne in 1377 on the death of his grandfather, Edward III, but his unpopularity had been growing since Richard's suppression of the Peasants' Revolt in 1381. He was increasingly criticised for his patronage of a few select royal favourites, to an extent that has been described as "lavish to the point of foolishness" by a biographer, historian Anthony Tuck. Parliament was also coming to the view that the King needed to rule as economically as was possible, and they observed with displeasure the King's distribution of extravagant patronage to a limited circle, the greatest recipient of which was Michael de la Pole, Earl of Suffolk. Furthermore, the Hundred Years' War was going poorly for England. Several expeditions had left for France in the early years of Richard's reign to defend English territory, but they were almost all military and political failures. In spite of these setbacks, parliament faced requests from the King for increased subsidies to pay for the war. The King was also unpopular because of his choice of advisers, particularly de la Pole, the chancellor, who was felt to exert too much influence on foreign policy and so became inextricably linked with its failure. One 20th-century historian, Clementine Oliver, has described de la Pole as a "staunch loyalist"; he had been elevated to the peerage as Earl of Suffolk only the previous year, the first of his family to receive a peerage. He advocated peace overtures to the French. Tuck has argued that, while probably the most sensible policy the government could have adopted, pacificism was unpopular with much of the English nobility, as a martial career such as their fathers had enjoyed was expected to be financially and chivalrically profitable. Some young nobles—such as the Earls of Arundel and Warwick—had "been kept in good humour since 1376 only by a lavish distribution of crown perquisites and war salaries", argues scholar M. V. Clarke".

In the event, as Tuck has said, subsequent royal attempts at a "policy of rapprochement with France made little headway". This may, combined with his uncle John of Gaunt's 1385 invasion of Castile, have provoked the planned French invasion of England of 1386. Further, France had recently renewed the Auld Alliance with Scotland, by which the former promised the latter an expeditionary force and 40,000 gold florins. Gaunt was the wealthiest man in England besides the king, and had often put his money to Richard's use. With Gaunt absent in Spain, he could use neither his wealth nor his retinue in defence of his nephew the King when the attacks of the Wonderful Parliament came. Either way, the war with France, being both exorbitantly expensive and producing few military successes for it, was the immediate cause of the parliament. For Richard, as historian J. S. Roskell put it, it also had the result of creating an "adversely critical attitude towards the government" that reflected negatively upon the King.

On top of the expense and failure of the campaign in France, the King urgently needed funds to defend the border with Scotland, and the kingdom from a possible French invasion. Medievalist Nigel Saul has argued that due to these threats, in summer 1386 "panic was taking hold of the south-eastern counties". The chronicler Thomas Walsingham described how like "timid mice they scurried hither and thither... This behaviour from men, who had showed up well in the tranquillity of peace with their fierce bravery, did not set an example to be followed of what should be done when they thought that battle was at hand and danger imminent." The absence of Gaunt probably increased the sense of hysteria. Gaunt was not to return to England for another three years, and Richard took advantage of Gaunt's absence to advance his favoured courtiers further up the peerage.

The previous parliament had attempted to force a commission upon the King in an effort to reform the royal household and especially its expenditure. This commission was effectively a regency council for the King. However, Richard limited the duration of the council's powers to one year, and it had expired by the time of the 1386 parliament. This commission criticised the King's distribution of patronage and also attempted to prevent him from elevating his choice of men to the ranks of the upper nobility. The King did not approve of the commission or its advice that he listen to more judicious counsellors, and ignored it. By the time parliament sat in October 1386, an atmosphere of political crisis was apparent to all.

No military successes had been achieved since the previous parliament, despite an extensive—and expensive—campaign in 1385. For the King personally, not only did he fall out badly with his uncle, John of Gaunt, but his financial and military impotence was exposed to all and sundry. If the campaign had been a success, on the other hand, then the king, as a returning conqueror would have drawn comparisons in martial prowess with his father and grandfather. By 1386, "the Commons had no good reason to overlook the excessive generosity of the King or to acquiesce in his government's arbitrary taxation" as historian John Palmer put it. Most of the criticisms raised by the 1386 parliament had already been complained of in that of 1385. Little had been done to resolve them by either King or chancellor, and when the 1386 parliament convened, continues Palmer, it "nursed a number of very substantial grievances".