I am afraid that I will have to both agree and disagree to some extent with many of the previous reviewers. I do agree that "La Reine Margot" (1994) from Patrice Chéreau was better by far than this film. However, the latter covers (or tries to cover) the whole life of Henri of Bourbon, who became King of Navarre in 1572 after the death of his mother Jeanne d'Albret, and then King of France after the assassination of Henri III, the last living son of Catherine of Medici and Henri II. The former focuses on a single episode - the massacre of the Saint Barthélemy - and what happened a few months before and a few months afterwards.
Neither film is historically accurate, but Henry of Navarre is - by far - the worst of the two. There are several reasons for this. "Le Reine Margot" is based on the historical novel of Alexandre Dumas, the French Conn Inggulden of his time, if I can make such a comparison. In other words, it is based on a piece of historical fiction where the background is generally accurate even if some elements - such as the role played by La Mole (the Hughenot hero who really existed, by the way) - are mostly the result of the author's imagination. I have no problem whatsoever here, since "La Reine Margot" does not pretend to be historically accurate. On the other hand, Henry of Navarre is portrayed as being his "incredible true story" and this is where the problems begin.
First, the scene with Nostradamus coming up with his prophesy is made up. Nostradamus, at the time, lived in Paris and worked for Queen Catherine of Medici. That he would have travelled across the whole of France to see the son of his patron's mortal ennemy (Jeanne d'Albret) and make his prophesy is somewhat unlikely, to put it mildly. Then there is the fact that Jeanne d'Albret was poisoned, allegedly by a pair of gloves that Catherine had given her. This is, at least, what the Hughenots believed at the time, including Henry. There is nothing about this in the film, neither is there anything about Catherine's (rather well deserved) reputation of using poison to get rid of her opponents. Why did Henry and the Hughenots nevertheless accept to come to Paris despite their (very strong) reservations? This had partly to do with Admiral de Coligny's very good relations with Charles IX, who called him "his father", partly with the fact that the King had given them all safe conduct for them to attend Henry's weeding with Marguerite de Valois (the "Reine Margot" of the other film) and partly because anyway the Hughenots wanted and needed peace for they were losing the war against the Catholics. Apart from the weeding celebrations, the other elements, which had little to do about noble interests, are simply not mentioned. The piece on the actual massacre of the Saint Bartholomew is more or less ok. Marguerite de Valois did, in reality obtain Henry's life from both Charles IX, who was circumvented by his mother, and from Catherine and Henri did escape the massacre by taking refuge in the King's appartments. It is very, very doubtful that he went searching for his friends across the streets of Paris and much more likely that he never left the Louvre that night or the next morning. Henri de Guise, the main organizer and perpetrator of the massacre, got what he wanted: the life of Coligny whom he rended resposable for the assassination of his own father (François de Guise) almost ten years before. This is also omitted, despite being quite revealing because it was essentially vengeance, or a blood feud which was made worse because the three forces (the Hughenots, the Guise, and Catherine and Anjou) were battling each other to establish their dominance over the weak and influençable Charles IX. Catherine allied herself with Guise because she feared that Coligny's influence over the King, her son, would replace hers.
Then there is the aftermath. Henri of Navarre was a prisoner in the Louvre. He did escape, but I seem to remember that it was before the death of Charles IX (and whith his help) rather than after his death two years later in 1574. Then you had a few years of desultory warfare with the South Ouest of France and Languedoc being largely - but not entirely - dominated by the Hughenots and the rest of the country in the hands of either Henri III or of Henri Duke of Guise and his brothers (the Duke of Mayenne, who makes a fleeting appearance in the film, and the Cardinal de Guise, which we do not even hear about). In 1580, Henri III (former Duke of Anjou) sends Joyeuse, one of his favorites, who, by the way, was one of the best swordsmen of the Kingdom and not only the vain and effeminate dandy that his portrayed to be in the film, has to send the royal army after Henry of Navarre who had been making inroads. This largely happened under the pressure of the Guise faction who were accusing the King of going "soft" on the Hughenots and of being incapable of beating them. Joyeuse lost the battle at Courtras and got himself killed. Then there was a further period of eight years which are entirely ommited from the film until the year 1588 when Guise organized an insurrection and Paris rebelled in favor of his "Ligue", chased the King from Paris and obliged him to take refufe at Blois when he started to gather an army to retake his capital. As Henry of Navarre was also around with his army, Henry III and Catherine gave safe conducts to the Guise Henry and the Cardinal) to come to Blois where they had them assassinated. So, contrary to what the film shows, Guise was not killed in Paris and Catherine, who was fatally ill at the time, helped out her favorite son one last time by providing Guise with one of her ladies in waiting for the night before, to make sure that he would not change his mind and flee. Then there are a number of other episodes missing. In particular, the battles that Henry of Navarre had to fight after the assassination of Henri III (this piece, at least, is in the film) at Arques and at Ivry against the army of the League lead by Mayenne, the last of hte Guise brothers. Later on, after Henri had become King (and become a Catholic again), there were a number of conspiracies to assassinate him, all of which were more or less backed by Spanish gold, including one by Biron, whom Henry had made a marshall.
There are some good pieces, however, particularly towards the end of the film. One such is Henry's love relationship with Gabrielle d'Estrée and, more generally, his marriage with Mary of Medici, for her huge dowry at a time when the King's coffers were empty, the country impoverished by 30 years of on and off civil war and money was needed to fight against Spain. Gabrielle was poisoned, as shown in the film and there were quite a few people who had an interest in doing the deed, although the culprits were never publicly named.
Another claim made by some reviewers about this film is that it is "well acted". The least that can be said here is that some actors have be asked to play roles for which they were not entirely suitable. Charles IX, for instance, was 22 at the time of the Saint Bartholomew massacre. Henry of Navarre was 19. Neither actor, whatever their qualities, looks the part. Even worse, the actor impersonating Anjou/Henri III makes him look like a coward and a whimp: he was neither. The actors playing Henri de Guise and Catherine de Medici do not even look physically alike their characters (neither does Charles the Ninth, by the way). Julien Boisselier as Henry of Navarre is better, but he seems to be in his mid thirties to mid fourties all through the film (Henry was 57 when he was kniffed by Ravaillac) and, apart from a bit of grey and white at the temples, he simply does not age during the film. Daniel Auteuil playing Henry of Navarre in "La Reine Margot" also did not look like being 19. However, Guise, Anjou, King Charles IX and Catherine were all much better in "La Reine Margot".
Amusingly, the "boobs" pieces are perhaps among those that may be the most accurate although, even there, Henry of Navarre's appetites seem to have largely developed after the massacre of the Saint Bathelémy, rather than before. The scene of Henry looking under the skirts of paysant girls in echange of a coin is, of course, made up. Note also that the nobles at the time had rather loose morals, although the Hughenots perhaps somewhat less than the Catholics. Henri de Guise was also known as being rather over fond of the ladies, for instance, and the two Henries were far from being the only ones. As another reviewer mentioned, even if somewhat inelegangly, Marguerite de Valois (the "Reine Margot") was a bit of a slut, buth then she had excuses: her brothers were not exactly pure little flowers and there were at least rumours that all three of them (including the youngest, François Duke of Alençon) had had sex with her, or even that they had raped her. Anyway, she was the mistress of Henri de Guise just before she got (very unwillingly) married to Henry of Navarre. As for Gabrielle (and all of the other noble mistresses of Henry of Navarre which are not mentioned in the film), she was, at least initially, in for what she could get out from the King: money, titles etc..., although, after a while, there might have been mutual love between the two. There certainly was on Henry's side. He may have developed some affection for Marguerite of Valois also, at least initially, although he did lock her up and never forgave her for knowing about the St Barthelemy massacre and not warning him in advance. He, rather understantably and unsurprisingly, felt that he could nver trust her again. This is something that the film shows rather well. Henry's relationship with Mary of Medici was not a happy one, as also well shown in the film. However, that the Florentine princess would chase him around and hit him in his mistress' room is somewhat difficult to believe, to put it mildly. What is correct, however, is that Henry delayed her coronation for a long time, and was assassinated shortly after it had happened. Hence the film's suggestion that she might have had something to do with it, but nothing has ever been proven and there was a rather large number of other powerful people who could have been behind the plot anyway.
Given all this, I am afraid that I cannot share the other reviewers' enthusiasm for this film. I did not like it and I therefore cannot really recommend it. A pity, because it could have been much, much better...