Xena and Gabrielle
The Original Subtext, as this site defines it; the most publically acknowledged, and most vehemently considered "real" by many viewers. The two women share a bond which is much deeper than mere friendship; to deny that is to deny a core element of the show. Their intimacy alone leads many to believe that there is a more-than-platonic level to their relationship, one which can be romantic or sexual or both. Certainly it is undeniable that Gabrielle and Xena's souls find one another over and over, life after life, and protect and cherish one another. They are soulmates in the truest sense of the word. For many, being soulmates is equivalent to being lovers, and thus this is seen as irrefutable proof of the women's love affair.
In addition to the basic intimacy and togetherness that Xena and Gabrielle share, the series has showcased several elements which have been deliberately ambiguous; some of these have been jokes, such as Joxer asking Xena if that's a hickey on her neck and not noticing as Gabrielle and Xena both look uncomfortable. Other elements have been looks, touches, and even vocal declarations of love. Whether they are openly revealing their romantic devotion to one another, or reaffirming their sisterly feelings, is not openly said. To those who believe the former, it is inarguable. To those who believe the latter, the same can be said.
Because the show has not said outright what position the two ladies are in, I (as an individual, as well as the one running this website) withhold an opinion. Certainly neither woman has had as lasting and strong a bond with any other romantic possibilities, including Gabrielle's marriage to Perdicus. On the other hand, if Xena and Gabrielle are openly lovers, they both do seem to flirt with other men more often than I'd be comfortable with my soulmate doing. ^_~ At this time, I think either option is possible, as there are certainly signs in both directions.
A post-show post-script: As I've mentioned elsewhere on this site, I don't generally acknowledge the sixth season (for various reasons). But in this section I feel it's important to include it in some examinations of the relationships, particularly that of Xena's and Gab's. From the limited amount of interaction I saw during the final season, I do feel that their relationship is less ambiguous at this point, and more strongly points toward a romantic involvement, particularly during what I saw of the series finale. The final season saw both the elimination of the majority of recurring characters with whom Xena and Gab used to interact with, and the intense strengthening of the bond between the two heroes; it would be easy to say that their relationship was finally consummated "off-screen" during this season. Without a definite confirmation, I still don't consider it an absolute fact, but it was certainly much less "sub" than in earlier seasons.