A Study of JNJ-78934804 in Participants With Moderately to Severely Active Ulcerative Colitis

Inclusion criteria:

* Diagnosis of ulcerative colitis (UC) established at least 12 weeks before screening including both endoscopic evidence and a histopathology report consistent with a diagnosis of UC.
* Moderately to severely active UC defined as baseline (Week 0) modified Mayo score of 5 to 9, inclusive, using the Mayo endoscopy subscore obtained during central review of the screening video endoscopy
* An endoscopy subscore \>=2 as obtained during central review of the screening video endoscopy
* Have had an inadequate initial response, loss of response, or intolerance to previous approved systemic therapies

Exclusion criteria:

* Isolated proctitis (UC limited to the rectum only or to less than \[\<\] 20 centimeter \[cm\] from the anal verge) as determined during central review of the screening video endoscopy OR Has a diagnosis of isolated proctitis
* Diagnosis of indeterminate colitis, microscopic colitis, ischemic colitis, Crohn's colitis or any findings suggestive of CD
* Has a history of or ongoing chronic or recurrent infectious disease
* Has previously demonstrated inadequate initial response, loss of response, allergy, hypersensitivity or intolerance to guselkumab or to golimumab
* Is a participant who is pregnant, breastfeeding, or planning to become pregnant, or plans to father a child, while enrolled in this study or within 6 months after the last dose of study intervention