A biological sample collection system includes a sample collection vessel having an opening disposed at a top portion thereof and a sample collection chamber having sample preservation reagent disposed therein and which is in fluid communication with the opening. The system additionally includes a funnel configured to selectively couple to the opening such that the funnel opening and the opening of the sample collection vessel are in fluid communication when the funnel coupled to the opening. The system also includes a removable stopper having a plug that is configured to seal the opening and/or the funnel opening. In some embodiments, a biological sample collection system includes a sample collection chamber having an opening disposed at a top portion thereof, a sample preservation reagent disposed with in the sample collection chamber, a funnel configured to selectively couple to the opening and including a ramp, and a removable stopper having a plug configured to seal the opening and a tapered ridge configured to selectively engage the ramp.
