Company: RNLXY
Filing Date: 2025-07-29
Form Type: POS AM
Source: 0001213900-25-068772
Chunk: 0

Company: Renalytix plc
Filing Date: 2025-07-29
Form: POS AM
Chunk 0
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<div align='center'>As filed with the Securities and Exchange Commission on July 29, 2025</div>

Registration No. 333-278765

<div align='center'>UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Post-Effective Amendment No. 1

to

Form S-3 Registration Statement

UNDER

THE SECURITIES ACT OF 1933

Renalytix plc

(Exact name of registrant as specified in its charter)</div>

| England and Wales               |     | Not Applicable         |
| (State or other jurisdiction of |     | (I.R.S. Employer       |
| incorporation or organization)  |     | Identification Number) |

<div align='center'>2 Leman Street

London E1W 9US

United Kingdom

Tel: +44 20 3139 2910

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Renalytix AI, Inc.

1460 Broadway

New York, NY 10036

Tel: +1 646 397 3970

(Name, address and telephone number of agent for service)

Copies of all communications, including communications sent to agent for service, should be sent to:</div>

| Mark E. Rosenstein                     |
| Stevens & Lee PC                       |
| 620 Freedom Business Center, Suite 200 |
| King of Prussia, PA 19406              |
| +1 610 205-6050                        |

APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: This post-effective amendment is being filed to deregister the unsold securities previously registered under this Registration Statement.

If the only securities being registered on this Form are being
offered pursuant to dividend or interest reinvestment plans, please check the following box. ☐

If any of the securities being registered on this Form are to be
offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 other than securities offered only in
connection with dividend or interest reinvestment plans, check the following box. ☐

If this Form is filed to register additional securities for an
offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration
statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a